Sendmail defers mails with attachments


Sendmail on CentOS, standard default config, worked fine for years on that machine, suddenly starts deferring mails with attachments for 72 hours. Restarting Apache and Sendmail a couple of times fixes the problem and it works normally for a couple of weeks, then does this abnormal deferring again.

What could be the reason for that?

EQ Admin

EQ Forum Admin
Staff member
Are you running out of any resources such as memory or disk space?

Next time try to narrow it down.

Do you really need to restart apache?

Does restarting sendmail fix the problem?

Is the server doing anything else with emails such as SpamAssassin content filtering or ClamAV virus scanning?

Does it matter what size the attachments are when they stop failing?

Do regular emails send OK when the attachments are failing?

What is sending the emails? Is it a web form and that's why you're restarting apache too?


TOP shows nothing that would normally worry me.
Just stopping sendmail and restarting it a few minutes later did not help.
Yes, SpamAssassin, recently updated, is on board. Has been since the machine was set up 3-4 years ago and on the previous ones. No changes there either.
Yes, plain text mails with no attachments go through instantly, from same sender to same recipient.
When sendmail has that attachment hysteria, it defers all mails with attachments.
Routine fax-to-email mails, same as for the last dozen years, test mails with small attachments, basically anything, that has an attachment.
After stopping sendmail and apache, with a 5 minute pause before restarting them, sendmail works again the way it is supposed to, as if nothing had ever happened.

mailQueue shows some deferred mails, but nothing outrageous. When there is a net problem somewhere, then some of the daily mailing lists generate pretty scary mailqueues, but the server handles those without a problem.