[CentOS] sendmail Deferred mail - reason unknown

Sean Carolan scarolan at gmail.com
Mon Dec 15 16:15:15 UTC 2008

I'm a bit baffled by this problem.  Maybe there's a sendmail guru out there
who can help me out here.  We have some end-users who need to receive
system-generated mail that originates from a java-based application on our
network.  The java app sends the mail through our sendmail cluster, which
then sends the email on to the end-user over the Internet.  The size of the
emails can range from a few kb up through around 2Mb in size.

The mail logs show that these emails are typically delayed for up to 24
hours, sometimes longer.  It appears that several attempts to deliver the
email are made, with each unsuccessful one showing "Deferred" status in the
maillog.  After several hours of failed attempts the mail finally goes
through successfully.  Here is a typical entry (customer name redacted):

exmx1 : Dec 14 05:28:39 exmx1 sendmail[31574]: mBDIYhEa031574: to=<
customer at example.com>, delay=00:00:00, xde
lay=00:00:00, mailer=esmtp, pri=41874, relay=mail.example.com., dsn=4.0.0,

Unfortunately there is no reason given for the "Deferred" status such as
"Server unavailable", etc.

Do you have any ideas how I can begin to troubleshoot this?
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