How to Fix “503 valid RCPT Command Must Precede DATA” Error

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Help meFor those that are tearing their hair out when getting the “503 valid RCPT command must precede DATA” error (we’ll refer to it as simply the “503 error” going forwards) when trying to send email, here are some common solutions that will hopefully get you back up and running. If these don’t work, or you need more detail on any of these steps, please read the rest of this article, and its comments, for some more in-depth solutions.

Possible Solutions for Server Error 503

  • Apostrophes – remove any apostrophes (single quotes) or other non-alphabetic characters from your email account name(s).
  • VPN – if your system is trying to connect via a VPN network while you’re sending email, you may get this error. Try disconnecting the VPN before sending/ receiving mail.
  • Full mailbox – make sure the mailbox of the affected account is not full or has met/ exceeded its quota. You can uncheck the following option to make sure a copy of all your emails is not being left on the server (note that since the email will be downloaded to your PC after this setting change, you won’t be able to access your emails from another location if you do this). In Outlook, browse to Tools > Account Setting > More Settings > Advanced > Uncheck “leave a copy of this message on the server.”
  • SMTP port – use port 26 (instead of the default 25) for outgoing mail.
  • Server authentication – setup your outgoing mail to use outgoing server authentication (sends mail by logging in with your email address and password). In Outlook, browse to Tools > Account Settings > More Settings > Advanced and change the outgoing server to ‘Auto.’ Next, browse back to More settings > Outgoing server and check the “My outgoing server uses the same authentication as my incoming server” box. If you select to have Outlook “remember your password” you won’t have to type it in every time you send an email.
  • Sender matching – make sure you’re sending from the same email address that the recipient sees your email coming in as (ie. don’t make the “from” field differ from the email address used in your outgoing mail settings).
  • Outlook PST files – sometimes the 503 error will occur if you have a corrupt Outlook PST (mail archive) file. Try repairing the file.

If none of these approaches work, or you need more detail on a particular step, please read the rest of this article for some additional suggestions.

503 Valid RCPT Command Must Precede DATA

We recently got this RCPT to command error when trying to send an email in Outlook. The culprit? Apparently, this occurs when a server is expecting to receive mail before sending. This is usually results from server authentication priorities (for example, you attempt to send mail before your “spam filter” has finished its receiving process.)

Solutions to Resolve the 503 RCPT Error

  • Pop before SMTP — Run a check for new messages (F9 key in Outlook) before sending your message and restart and rerun your spam filter application. Your IP address is entered in a relay hosts file, allowing email to be sent from your address for up to half an hour.
  • If the problem still persists check “my server requires authentication” to authenticate automatically. With this setting, you can bypass the check above and send mail without having to “pop” your mailbox first. You can also try changing the outgoing port from 25 to 26, since some ISP’s block this port.
  • Several of our readers have pointed out that it may help to remove apostrophes from your email account names (and ask senders to remove them if you’re having trouble receiving emails from them).
  • If you’re on a VPN, try disconnecting from the VPN prior to using your mail program.
  • Your mailbox may be full – try clearing out messages or asking your mail service provider to increase your mailbox limits.
  • If you are using multiple mailboxes, make sure these fixes/settings are applied to each one of them, especially the “default” one.
  • Finally, if using a mail screening utility such as Mail Washer, you may want to disable the “automatically check at intervals” setting and check mail manually. If the system checks mail while you are sending you may get this error.

Still Having Trouble?

If none of the above work we recommend contacting your hosting provider. Your mail services account needs to be set up properly (associated with the right username, etc.). We encountered this exact problem when switching hosts once – the mail server configuration got goofed up, and none of the above solutions worked. In the interim (until settings are fixed by your hosting provider) you can adjust your outgoing mail server to reflect that which your ISP uses, which should let you send mail again through your local client (Outlook, but not from the server (Webmail), until the problem is fixed.

As mentioned previously, to keep your mail system running smoothly, and to help you get rid of various email related errors, including the 503 valid RCPT error, we recommend installing a solid anti-spam solution. Anti-spam software is affordable, but your email and privacy are priceless. Don’t let the spammers get the best of you. And be sure to check out more troubleshooting tips.

Have you had this issue before?

About The Author:

Alex has been involved on the business side of the internet since the early 2000's. He holds both a Management Science degree from the University of California at San Diego as well as a Computer Science degree from NJIT.

We Rock Your Web had its roots back in 2004 as the tech blog for a web design and development company Alex founded that has grown and evolved into the parent company of We Rock Your Web.

While his foundation is rooted in web development, his expertise today lies in content and digital marketing, SEO, organic and paid search, analytics, and publishing. Alex is an avid tennis player, nature enthusiast, and hiker, and enjoys spending time with his wife, friends, and dogs.

Disclaimer: This website contains reviews, opinions and information regarding products and services manufactured or provided by third parties. We are not responsible in any way for such products and services, and nothing contained here should be construed as a guarantee of the functionality, utility, safety or reliability of any product or services reviewed or discussed. Please follow the directions provided by the manufacturer or service provider when using any product or service reviewed or discussed on this website.

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newest oldest most voted
Thanks; this worked •If the problem still persists check “my server requires authentication” to authenticate automatically
my challenge is that i can still send emails to another outlook accounts but not Gmail and anything that’s not outlook
Robert Mark
To fix the 503 valid Rcpt command precede data error the user needs to change the SMTP and do the process of the valid authentication on the advance tab.
I just found out that my new web host’s servers don’t work with the combination of Windows 7 and Outlook 2010. I was given the choice to move to older servers but I opted not to do that. Instead, I’m going to break away from Outlook entirely and use Thunderbird. It’s free, super easy to use because it does the settings for you, and was recommended by a tech at the hosting company who has used it for over a decade.

Mozilla actually just launched the new site yesterday, which indicates their commitment to supporting it in the future.

This was awesome instructions are great didnt take me more than 5minutes to solve the problem thank you so much !!!
Kimberly Alt (Admin)
Glad we could help!
Found another cause of this problem. I had an attachment with rounded brackets in the file name. A word docx. Thanks for the help, it sort of took me in the right direction with the note about the apostrophes…
“Use same settings as my incoming mail server” solved my problem
What is a 503 error? I don’t understand why there is a number associated with it, are there other 503 errors that are not related to this “valid RCPT command must precede data”
Jeff Butler (Admin)
503 errors basically mean that the server of the web site you are trying to connect to is not available. So to answer your question specifically, yes there are many more 503 errors than just this specific one.
Lutaaya Gad
it really worked for me. thank you very much i.e server authentication
Empty your email box, this solved my problem.
Removing non-alpha characters from my account name resolved the 503 issue. Thanks, Alex!
Andrzej Cojg
It is also worth noting that Outlook might have some difficulties while sending your message if your password consists of certain special symbols. In my workplace, using capital, small letters, numbers and symbols is a must for overblown security reasons. Reset your password to something less challenging and try again.

Side note: This problem could be related to your system language and coding (unicode, ansii, utf-8).

Open Outlook click on Tools(2007) / File(2010) > Account Settings > Highlight the email account > Change > More settings > Outgoing server > Check the box ‘My outgoing server (SMTP) requires authentication’ > Verify that the circle-box ‘Use same settings as my incoming mail server’ is selected.
Carina De Almeida
Thanks Alex – port 26 did the trick!
I suddenly got this error message yesterday after years of doing nothing different! The server authentication (email address / password) was duly added and now it works – go figure!
Boba Fett
Boom! Port setting worked like a charm! Thanks.
Hussein Aladin
This helped a lot. Changed the server authentication to “auto” and now I am able to send outgoing mails. Thanks!!
Kimberly Alt (Admin)
Glad this solution worked for you! Thanks for letting us know about your success!
I’m trying to set up my website email through just host and getting a 503 error when receiving emails. When I use a gmail account to send to my domain address email, I receive “503 This mail server requires authentication when attempting to send to a non-local e-mail address”. I tried looking everywhere and no matter what I do I can’t receive emails. Any help would be appreciated! Thank you.
Kimberly Alt (Admin)
Is there any more information you can give us about your problem?
Great help…one of the suggestions worked! Thank you.
Kimberly Alt (Admin)
You’re welcome! Glad we could help!
No help – bunch of technical jargon.
Kimberly Alt (Admin)
Is there a question you have that we can help you with? If you’d like, you can explain your problem in detail and we may be able to explain it in another way to solve your problem.
Got it! Server auth and/or SMTP port change did the trick!
Hi, I have checked with authentication of SMTP and I have changed the SMTP port also from 25 to 26 then also i cant able to send or receive any emails. Please help me out from this issue.

Madhavan R
Hi. As you had advised i had repaired the PST file for four hours (10 GB) and then found the same error occurring again, i deleted and re-configured the email id in the Microsoft Outlook that simply solved the error. Thought authentication – we use authentication mode for our outlook. Any ways, thanks a lot for your post and support!

I just changed the port and it worked for me. Thanks!

thank u, it works!

Changing the port to 26 and it worked. Thank you!

This worked for me!

Server authentication – setup your outgoing mail to use outgoing server authentication (sends mail by logging in with your email address and password).

After testing all the above and nothing solved it. It turns out that our ISP (Telepacific) was blacklisting our domain/server and they said that a pc at our office was probably sending a lot of spam. We checked and it turns out that all the antivirus were working, active and updated, so they took us OFF the blacklist and the problem was solved.

Rosie Page
Reload the web page. Then click the ‘Reload this page’ icon in the browser and press F5 key on the keyboard. Enter the URL on the browser’s address bar and load the page again. Clear your browser’s cache, delete your browser’s cookies. And finally, restart your browser. For more, consult with
My outlook gave this error message, so I followed the steps above, changed to secure authentication and so on, it got worse, so I unchecked the authentication again and now it’s working just fine.

Does that equal beating the system over the head and then it wants to work?

I don’t get it, but something helped.


Changing SMTP port – use port 26 (instead of the default 25) for outgoing mail.

& Server authentication worked for me.

Many thanks!

Kimberly Alt
Glad to hear it worked for you Vicki! Thanks for reading and commenting.
a web rocker
thanks for sharing.. very helpful!

a web rocker
thank you friend you’ve solved my problem

I have seen a few errors where people have mentioned that the only get this error when replying or forwarding and NOT when they create a brand new email. This actually is very easy to resolve and is simply an Outlook Client oversight.

If you have multiple mailboxes, much like I do set-up to send and receive within your email client (I have 5 e.g. and and etc) then each of these mailboxes need to have the box for “my server requires authentication” ticked.

Check each and every mailbox account you have setup to send and receive in Outlook as this is the problem. Why is this happening? Well, even though your default mailbox is set in Outlook (mine is – if someone sends an email to, for example, your email address, then you click forward or reply, Outlook will then use your account to send the mail. If this account has not got the outgoing “my server requires authentication” box ticked, then you will get this error.

Like me, I never send email from my email address, all emails get sent from my default mailbox so you are led to believe it is an error with your default mailbox but the clue is in the email when you are forwarding or replying – just above the To: line in the forwarding email you will see a blue box which says : “this message will be sent via“. So, to recap, be careful when replying or forwarding to emails which were sent to your other mailboxes and ensure that those mailboxes also have the correct settings; ie. set the same as your default primary mailbox in Outlook ๐Ÿ™‚

Alex Schenker
This is one of the best explanations we’ve heard on this error. Thanks so much for taking the time to share with our community members, your time is much appreciated!!

Thank you very much for sharing this helpful information. I think that your advice did the “trick” for me. Have a fantastic day!


Ralph Flores

US – San Diego, CA

Thank you so much, your advice was spot on. I have been trying to send emails for ages. The moment I took your advice they started going through. Thanks again!

This was right on the money with the issue I was experiencing! Thanks again web rocker!

Nicky A
I’ve spent the last 4 hours trying to solve this problem. My outlook was working fine yesterday and today nothing. I hate computers and find it all very high tech. I had tried everything, read several online solutions and nothing was working. I have two mailbox accounts and your solution was spot on. Big sigh of relief here. Thank you!

Kimberly Alt
Nicky I’m so glad this forum could help you! Thanks for reading and happy emailing ๐Ÿ™‚

I think just make sure from your service provider that you can use port 26 for SMTP.



After going to and spending several HOURS of my Friday night and into Saturday morning looking for the reason and fix for this problem, I finally landed here on your website and voila! The solution!! THANK YOU!!

I can now go to bed and know that my business will be functioning smoothly again when I get up in the morning.

Too bad Microsoft couldn’t have provided me with this information sooner. ๐Ÿ™

I’ve bookmarked your website for future reference and plan to share it with others. ๐Ÿ™‚

Alex Schenker
That’s great to hear! We’re glad you got your business back up and running and were able to get some sleep ๐Ÿ˜‰

Thanks for bookmarking us. We’re working hard to keep quality content and web/IT solutions coming your way.

Once I had an unpleasant situation with my Outlook pst files. Luckily I found a good solution – pst repair, which took care of my Outlook errors and made my email program run better.

The contents here are excellent.

The solution to 503 problem:

1. Uncheck the ‘Tools->Account Setting->More settings->Advanced’ page’s Delivery ‘Leave a copy of…’ so that the server space is freed once you download a mail successfully.

2. No single quotes in the names of the recipients (MS never thought of that for that matter)

3. (This is what worked for me) Go to ‘Tools->Account Setting->More settings->Advanced’ and change the outgoing server to ‘Auto’ and again change ‘Tools->Account Setting->More settings->Outgoing server’ and check on the ‘My outgoing server uses the same authentication as my incoming server’ on. If you have set not to remember passwords, even while sending the password will be prompted for but you will not get the 503 error.


Dr. Kasivishvanathan Sundar

How did I solve it?

Check for the space allocated on server for inbox mail.

The mail box had 50mb maximum and it was full. Didn’t cross my mind until I sent an e-mail from my other mailbox on the same server.

So as a solution, verify the mailbox disk space from the server side.

Horatiu I

Thanks for the article. First suggestion I tried worked for my users. ๐Ÿ™‚

Wow that was annoying to deal with. Thanks so much for addressing the issue – I’m hoping I won’t be seeing the 503 problem creep up again – fingers crossed!

Thanks for the info on your site! Saved me ๐Ÿ™‚

Many thanks for the info on your website… worked a treat.


I am having the same 503 error sending email to anyone with a – in the name like I tried to send from our company server and earthlink with the same results.
I have started to frequently get this error, when I try to send email from outlook 2003
The following recipient(s) could not be reached:
‘’ on 03/08/2007 10:48
503 valid RCPT command must precede DATA
This doesn’t happen every time, but frequently. Do you know what the error means and what I can do to correct it?
Hi there,

Please take a look at our article above for some updated suggestions in helping you resolve the 503 error. You might also want to try removing apostrophe’s from your email account names.

I got this message and it turned out to be related to my mailbox being full. After my limits were increased the problem resolved itself.

I got this error when sending email while I was VPN’ing to another network – I had forgotten to disconnect the VPN connection first.

We got the 503 error message on our email system and found that it was because the recipient had an apostrophe in their account name. As he was one of internal recipients, we have removed the apostrophe, ie (from Oneill to Neill). I spoke with Microsoft and they blamed the ISP. I talked to the ISP, and they blamed Microsoft. I need a second opinion, and I need help to solve this problem. Your help would be greatly appreciated.

Thank you

Gloria Fanucci

My email had been working fine for quite some time now and today every 2nd email I send gives me the 503 error.

I tried everything, but noticed that “My outgoing server (SMTP) requires authentication” was not checked, so I checked it, but now when i click next is wants to send a test email and then i get this error:

Send test email message: None of the authentication methods supported by this client are supported by your server.

Now I just don’t know what to do. Please help!

Giles Tennick
After the wife managed to spill tea all over my work laptop, I had to swap over to the old desktop and my outlook settings were almost working apart from this error on sending emails. Was getting super frustrated so a huge thank you to whoever wrote this thread, I really appreciate it!!

Come on! Don’t blame your wife for the tea while it’s your laptop and you are probably responsible for the spill. Even though your wife spilled it, you should be ashamed of blaming her here on this forum.

a web rocker
I went through all of the above fixes and none of them worked for me. I was getting the error trying to send email from a web page using ASP/VB & ASPEmail. I actually found the fix on another site that said the following:

Most probably, this error means your script is not calling any of these methods:


As a result, AspEmail gets no recipient addresses to send a message to. Check the logic of your code. If you are calling AddAddress/AddCC/AddBcc in a loop, make sure the body of the loop is entered at least once.

For example, if you are looping through a recordset to obtain your recipient addresses, make sure your database query returns at least one record.

After checking my variable for AddAddress, which I did have in the code, I found that the address was not getting populated so I tried it by hardcoding the email address to set it. And voila! It worked. So, now I have to go back through my code to see why it’s not being set but at least I know what’s wrong. Thanks for the extra guidance though! Hopefully this helps another lost soul…


Mark E
My error appears to fall into the uncommon faults. 503 valid RCPT command must precede DATA. My email was workin fine for the last 3 weeks whilst in the UK, now I am back at work in Iraq I can no longer send emails, this also happened before I went on leave so am assuming it has something to do with being abroad.

Can you please help.

Alex Schenker
Hi Mark,

Sorry you’re having troubles with your email. That is one of the peskiest errors to deal with. Can you give us some more details to help us troubleshoot? Such as:

Who is your ISP (Internet Service Provider) in Iraq?
What email program are you using (ie. Thunderbird, Outlook)?
What operating system (ie. Windows 7) are you using?

Mark E
Thanks for the quick response.

My ISP in Iraq is Rey Telecom, unfortunately I cannot get an answer from them at the moment as it’s their weekend. I am using Outlook on Windows 7 64-bit.



ps. This is being sent from my web mail.

Alex Schenker
Hi Mark,

I’m thinking maybe the problem is your smtp (outgoing) mail server address. In Outlook, navigate to the following:

Tools > Email Accounts > “View or change existing email accounts” > Select your account, and under “Server Information”, let me know what the Outgoing mail server (SMTP) is.

I’m guessing it’s set to use Blue Yonder (UK), whereas it should be set to those of Rey Telecom. If that’s not it, you might want to try enabling “Outgoing server authentication” (basically uses your username & password to send email). Rey Telecom should have details on how exactly this should be setup, given their requirements.

Let me know how it goes.

Mark E
I did not have Rey Telecoms smtp settings so I changed to “log on using” and it started working, absolutely amazing, can’t thank you enough, although I would like to understand the reasoning behind it, as I said previously, it was working fine a little over a month ago.

Thanks again, kindly let me know if you have received.



Alex Schenker
Hi Mark,

That’s fantastic. It’s becoming somewhat more common for ISP’s to require what’s called “outgoing server authentication.” Basically, using your email username and password to login each time you send an email. This helps prevent malicious users from being able to misuse outgoing mail servers (ie. use them to send their spam, etc.).

This is fantastic. I just changed the settings to authenticate the outgoing mail server. Since the problem is sorted. No more errors.

However, I understood although Outlook was showing an error, the email actually has been sent and also received by the recipients.

Thanks again for the very helpful hint.

euro 2012 tips
Finally, my outlook problem is solved. I was facing outgoing problems that are now fixed!

Phoenix in Tampa
Went right down your list and of fixes and found the problem in Server Authentication by changing the setting from None to Auto. Nice work – even a non-geek like me walked right through it.

Thank you so much! I had this problem when I was upgrading to Outlook from Outlook Express (which I couldn’t stand anymore). Everything went fine except for this error message that I got when composing a new mail (strange that when I was replying to a message from my inbox, it was okay). Step 5 “Server Authentication” fixed everything. Thanks again.

I keep getting this message when using my 3G card – tried all the changes you suggested – still not working …

Awesome. This totally helped me rock around the annoying 503 valid RCPT command failed error ๐Ÿ™‚

If you need help to rectify the 503 error totally, and to rectify queries which are taking much execution time, you may have a problem with a huge mysql database. You can contact me at pankajash at gmail dot com or info at netleon dot com for assistance.

I get the same 503 error code on AOL. How would you fix it on an America Online email account?

Alex Schenker
Hi there,

I’m sorry you’re having trouble with your AOL email account. We’ve added a bulleted list of steps at the top of the article since you posted your comment. Could you try them in succession and tell us if any of them work to help resolve your issue?

We just implemented a new vpn service and found that we started getting these 503 errors. It took us days to figure out what was wrong until we came across your blog! Thanks.

When I send an email to a specific domain, I get an error right away. This is what i get:

Your message did not reach some or all of the intended recipients.

Subject: test
Sent: 10/22/2007 10:25 AM

The following recipient(s) cannot be reached:

‘’ on 10/22/2007 10:25 AM
503 Valid RCPT command must precede DATA

…I changed the domain name for security purposes…

I Looked it up and all my settings on the Exchange server are ok. That domain is the only one i cant send to. I checked with the ISP and the PTR Record is ok. We also checked the MX record and that is Ok. When I send myself and email from the exchange server with the problem and i get the following error:

Your message did not reach some or all of the intended recipients.

Subject: test
Sent: 10/22/2007 9:42 AM

The following recipient(s) could not be reached: on 10/22/2007 9:42 AM
There was a SMTP communication problem with the recipient’s email server. Please contact your system administrator.

…I changed the domain name for secutiy purposes…

I have talked to Microsoft, they are blaming the ISP. I talked to the ISP and they blame Microsoft. So i need someone else’s opinion and I need help to fix this issue. Your Help will be greatly appreciated. Thanks

Hi there,

First off – you had forgotten to change your email address in the second example so I went ahead and did that for you.

The best way to diagnose this is to try and send to the email address from a different outgoing server. If you want I can try and send a test mail.

The fact that you’re getting the error right away indicates the mail is never being sent to begin with. Assuming you’ve already tried the suggestions mentioned in our article, you may also want to check that the DNS records for the domain have propagated. This error also occurs when trying to send email to an account that is setup on the server but does not have an active DNS record.

I recommend you contact your hosting provider (not necessarily the same company as your ISP) – they should be able to check your server configuration and resolve the issue.

we got this message on our email system and found it was because a recipient had an apostrophe in their account name. As it was an internal adressee we removed the apostrophe ie oneil not o’neil

we had 2 options

one, not to pick up the adressee from a drop down list that has account full name (including the offending apostrophe. Just type on the addressee manually.


two. Rename the email account without the apostrophe.

Very interesting, hadn’t heard of this one before. Thanks for the tip, I’m sure this will save a lot of our users a lot of headaches!