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Sender verify Failed

Posted: Fri Aug 31, 2007 8:55 am
by decipher
Hi There
I have been using Swiftmailer to send mass emails, and have recently checked my Mail Delievery Stats in the WHM.
There are a lot of :
Rejected RCPT: Sender verify failed
Rejected RCPT: Could not complete sender verify callout
I haven't been able to find much info on these log messages, what does this mean exactly?

Posted: Fri Aug 31, 2007 11:50 am
by Chris Corbyn
If these are just on the log list it might not be directly frm Swift (does that SMTP server take incoming mail too?). My SMTP is full of this too because spammers try sending emails to be from addresses that don't exist.

"Sender verify failed" means that your SMTP server could not find an MX record for the email address of the sender. As in: user@no-such-place.com.

"Could not complete sender verify callout" looks fishy. That suggests that your server is trying to verify addresses not only by using the MX record, but also by issuing a VRFY command to the remote server (checks if that server really has this user at it) -- that's blocked on most hosts these days to stop spammers obtaining lists of email addresses by force.

Posted: Tue Sep 04, 2007 5:46 am
by decipher
Hey man
Thanks for the reply. It does seem to be spammers gotten hold of my SMTP server. :( A couple of hundred "Sender verify failed" are popping up every day without me sending any mails.
Thanks for clearing it up ;)