Orphaned 'd' files in sendmail queue

[Balakumar M]

Can anyone help me understand how 'd' (data) files can become orphaned
in my sendmail queue?

Config is multiple sendmail boxes behind hardware vip. This acts as
relay for applications sending emails to known/registered customers,
so bad address volume is low. Sendmail servers run single queue.
Normally one will see this sort of thing:

# mailq | grep Total
Total requests: 105
# ls /var/spool/mqueue/ | grep -c ^d
105
# ls /var/spool/mqueue/ | grep -c ^q
105

But occasionally I will find that there are a significant number of
orphaned 'd' files, so I'll see something like this:

# mailq | grep Total
Total requests: 200
# ls /var/spool/mqueue/ | grep -c ^d
12406
# ls /var/spool/mqueue/ | grep -c ^q
200

Further investigation will show that the 'd' files with no
corresponding 'q' files are older than the sendmail retry timeout of
36 hours (sometimes they are a few weeks old even). Sometimes there is
a 'Q' file for the same message (what are these?), but most often
there only the 'd' file.

many of them will have a log such as this:

Jan 10 12:09:52 mail sendmail[18710]: m0AK9m5w018688: m0AK9q5v018710:
postmaster notify: Host unknown (Name server: somedomain.com: host not
found)
Jan 10 12:09:53 mail sendmail[18710]: m0AK9q5v018710: to=root,
delay=00:00:01, xdelay=00:00:01, mailer=local, pri=35234, dsn=5.0.0,
stat=Can't create output
Jan 10 12:09:53 mail sendmail[18710]: m0AK9q5v018710: m0AK9q5w018710:
return to sender: Can't create output
Jan 10 12:09:53 mail sendmail[18710]: m0AK9q5v018710: Losing ./
qfm0AK9q5v018710: savemail panic
Jan 10 12:09:53 mail sendmail[18710]: m0AK9q5v018710: SYSERR(root):
savemail: cannot save rejected email anywhere

Can anyone help me understand how this is happening?

[TTr]

It is very typical to end up with old "df" files in /var/mqueue. They are partial messages of aborted SMTP connections for a variety of reasons. You should delete anything that is older than 5 days (that is the 5-day undeliverable setting in sendmail).

You should probably use a "find /var/mqueeu -mtime ..." command to delete them.