I am using a combination of Postfix, Dovecot and Roundcube for a web mail system. I have a Google Apps for Domains account so am using Google's SMTP server for outgoing mail.

I noticed a couple of days ago my postfix logs reported a couple of deferred emails. On checking mailq there were a couple of entries like this (not exactly this one because they've been removed):

-Queue ID- --Size-- ----Arrival Time---- -Sender/Recipient------- 2A66F820CF 2889 Tue Jul 10 09:42:46 MAILER-DAEMON (SASL authentication failed; server smtp.gmail.com[] said: 535-5.7.8 Username and Password not accepted. Learn more at?535 5.7.8 https://support.google.com/mail/?p=BadCredentials w135-v6sm3873050wme.7 - gsmtp) donotreply@e.myyodel.co.uk

Yodel is a courier company in the UK and I had a couple of emails from them recently about a package being delivered. However, I did not reply to those emails, and there was no request for a read receipt or anything, so I wasn't sure where these emails in the queue had come from. I also don't know why they were being queued with the "bad credentials" error because I have no problem sending emails normally.

I deleted the two entries and I thought nothing else of it, until this morning when I noticed the entry above appeared again. As I haven't had any emails from Yodel since so this has got me more suspicious.

What could be creating these emails? I don't think it's malware as the fact I have genuinely received emails from Yodel recently make this unlikely.

  • could Yodel be attempting to send emails via your server and failing? – Sir Adelaide Jul 13 '18 at 5:39
  • @SirAdelaide it’s possible I suppose, but I read the mailq entry as email being sent to yodel. – Darren Jul 13 '18 at 6:40

You seem to forward messages to/via google without changing envelope sender email address
(as passed in MAIL FROM: in SMTP session).

It makes your server send bounces (reports about delivery problem) to/via google to unchanged original envelope sender.

  • Thanks for the answer, but I'm not sure I follow what you're saying. There shouldn't be any delivery problems creating a bounce as I didn't reply to the emails I received (and obviously the ones I received arrived OK). – Darren Jul 11 '18 at 9:33
  • Most likely It may be caused by email alias in you MTA/postfix configuration or some user's ~/.forward file. – AnFi Jul 11 '18 at 9:39
  • No, there are no .forward files in use or aliases that would explain this. – Darren Jul 11 '18 at 9:41

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.