How To Fix “503 Valid RCPT Command Must Precede DATA” Error

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Man banging on table with frustration (caption: How To Fix "503 Valid RCPT Command Must Precede DATA")For 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 the comments below, for some more in-depth solutions.

Possible Causes And Solutions For Email Error 503

There are several possible causes your email client might give you the error 503 valid RCPT command must precede DATA (and subsequently you won’t be able to send or receive email). Here are the most common causes and their solutions.


Remove any apostrophes (single quotes) or other non-alphabetic characters from your email account name(s).

Full Mailbox

Make sure the mailbox of the affected account is not full or has met or 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.”

Multiple Mailboxes

If you are using multiple mailboxes, make sure these fixes/settings are applied to each one of them, especially the “default” one.

Outlook PST Files

Sometimes the 503 error will occur if you have a corrupt Outlook PST (mail archive) file. Try repairing the file.

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.

Receive Before Send

Your server may expect to receive mail before sending. This usually results from server authentication priorities (for example, you attempt to send mail before your “spam filter” has finished its receiving process.)


Try using port 26 (this is used for secure/authenticated connections, instead of the default 25) for outgoing mail.

Email windowSender 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).

Server Authentication

Set up 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.

Spam Checkers

Best VPN service with keyboardIf 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.


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 and receiving mail.

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.

Got any other email troubles you need help with? Our experts will find the answer for you (for example, helping you if you’re having trouble getting your Gmail to load). Just ask us in the comments below.

Did our solutions get your 503 error resolved?

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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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

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 !!!

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”

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.

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!

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.

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!

Boom! Port setting worked like a charm! Thanks.

This helped a lot. Changed the server authentication to “auto” and now I am able to send outgoing mails. Thanks!!

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.

Is there any more information you can give us about your problem?

Great help…one of the suggestions worked! Thank you.

You’re welcome! Glad we could help!

No help – bunch of technical jargon.

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!

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

& Server authentication worked for me.

Many thanks!

Glad to hear it worked for you Vicki! Thanks for reading and commenting.

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.


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.

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

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).