A few days ago, my email on Outlook started to have issues. I was able to send emails just fine, but there was an issue with receiving emails. People were telling me the email they sent to me would bounce back, giving them “Mail delivery failed: returning message to sender” error. Testing it myself, it turned out that some emails were received successfully by my email client, but most of them were returned back showing that SMTP error 553. In this post, I will show you what I tried and what finally worked for me to solve this issue.
The error message contained in the bounced email had the subject Fwd: Mail delivery failed: returning message to sender and contained the following error:
553 sorry, that domain isn't in my list of allowed rcpthosts (#5.7.1)
Looking for answers on the web, This seems to happen when a mail server refuses to act as a relay. I found several suggestions on how to fix this error. Unfortunately, those suggestions were intended for people getting the 553 SMTP error message while sending the email. They had no problem receiving emails. In my case, I was sending emails just fine, receiving the emails did not work as it should. If you have the same issue as me, then skip to the next section.
If you get bounced email with 553 error while sending email, try one of the suggestions below. For step by step instructions on how to accomplish these changes in Microsoft Outlook 2013, check this AuthSMTP article.
- Turn on SMTP requires Authentication option
Since most mail servers require an authentication, this error could happen when the sender has SMTP authentication turned off. In AuthSMTP article, this is shown in step 6.
- Set SMTP port from 25 to 587
In AuthSMTP article, this is shown in step 7.
- Toggle SPA (secure password authentication)
In AuthSMTP article, this option can be found on the Change Account window shown in step 4.
If nothing of the above worked for you, and the problem occurs only when sending email to specific domain (part of email after @) then the problem is most probably at the recipient’s end.
Contacting hosting provider
Unable to find the solution online, I decided to contact the support of my hosting provider. In the end it turned out, that the problem was with them. The hosting provider migrated my domains to a new server, but didn’t set configuration correctly, so some of the emails were still being redirected to the old server. As my domain was now missing in the old server, those emails were bounced back to the sender with an SMTP 553 error. This makes sense since some mail administrators use the 553 error if a user doesn't exist.
When tackling 553 SMTP email error, most suggestions found on the web is focused on what sender getting this error should do. They are listed in this article, but the cause of the problem could also be on the recipient’s end, as it was in my case. It turned out the problem was not with my email client Microsoft Outlook, but with my hosting provider. Contacting them about this problem solved the issue.
How did you solve your 553 SMTP issue? Drop a comment and let us know. If you found this article useful, consider sharing it on social networks.