I seem to have a problem configuring my Microsoft Exchange to send mails outisde of the domain. I have setup my smtp connectors and everything else. I can receive mails but I can't seem to send any. I keep getting #5.5.0 smtp;550 Sender verify failed

Anyone has an idea how I could fix that?



  • How is your sending setup configured? Do you try using a relay? Private ISP that blocks outgoing SMTP? Bad SPF record that does not match your IP / Server name? Reverse DNS mapping set up? – TomTom Mar 23 '10 at 9:43
  • Well, I am using my ISP smtp server to send mails. My domain is pointing to the exchange server. I have setup my logs for the default smtp server but not sure what is what in there. I keep getting 250 and 240 (which I assume is normal). I am thinking it might be my isp smtp blocking me from sending through them. – Yves Mar 23 '10 at 9:53

This sort of error is usually related the the receiving mail server denying your mail for anti-spam reasons, so it's a little odd that you cannot send any mail at all, normally there are some mail servers who will happily accept any old mail.

Anyway, things to check here are that your IP is not on a blacklist, that you have a proper RDNS record setup for your domain. As you state you are using your ISP's smtp server to send outgoing mail, you may want to check with them to see if they can explain why it's not working correctly.

  • It definitely sounds like something with the ISP's STMP server. From the message you got back, it sounds like they might require the from address be of the ISP (ie, to use Comcast SMTP servers, you have to be sending from a comcast.net address). If you're using your own domain, they might now allow that. It could also be authentication problems with how you connect to the ISP SMTP servers. P.S. - Comcast does allow any domain for its SMTP server, btw. – Paul Kroon Jun 2 '10 at 0:37

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.