How to Resolve Outlook Error Code 503?

When sending email, if you receive an immediate bounceback, such as the following:
The following recipient(s) could not be reached:
‘John Smith’ on DATE/DATE/DATE
that means you get Outlook error 503. below are some solution that helps the user to solve this error problem.

Solutions to Resolve the 503 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.
    Here, are some solution for 503 Error
  • Apostrophes– remove any apostrophes (single quotes) or other non-alphabetic characters from your email account name.
  • 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.

Steps to fix Outlook Error 503 According to their Outlook version-

In Outlook 2003-

Step-1 In the first step, click Tools at the top bar and select Options.

Step-2 Choose the Mail Setup tab from the Options box and click E-mail Accounts.

Step-3 Select the email account you are trying to send mail from and click Next. To allow outgoing authentication in Outlook 2003, check the My outgoing server (SMTP) requires authentication box.

Leave the Use same settings as my incoming mail server box dotted.

In Outlook 2007-

Step-1 click Tools at the top bar, and select Account Settings.

Step-2 In the Account Settings window, on the E-mail tab, select the appropriate email account and click Change.

Step-3 Now, Click More Settings.

Step-4 This will put you on the General tab of the Internet E-mail Settings.

Step-5 Click the Outgoing Server tab. Check the My outgoing server (SMTP) requires authentication box.


In Outlook 2010-

Step-1 In the first step click File and after this go to Account Settings.

Step-2 Click Account Settings again and select the E-mail tab.

Step-3 Select the email account with sending error and click Change. In the Account window, select More Settings.

Step-4 In the Internet E-mail Settings window, click the Outgoing Server tab and click the My outgoing server (SMTP) requires authentication box.


In Outlook 2013-

Step-1 In the first step go to Tools and after this go to Account Settings.

Step-2 Double click the email account you wish to correct. Next, click More Settings.

Step-3 For Internet E-mail Settings, select the Outgoing Server tab.

Step-4 Check the My outgoing server (SMTP) requires authentication box.

Step-5 Click OK.

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