Twice in the last few days, I've gotten a message in my sendmail logs that looks
like this:

Sep  6 06:59:59 jik2 sendmail[2513]: l81MB8Ms007747: queueup: cannot create
./tfl81MB8Ms007747, uid=0: File exists

In both cases, the message occurred while trying to send a bounce message.  In
both cases, the message being bounced was a piece of spam, and sendmail had
already been trying to send the bounce for several days, but it wasn't sending
because of course the return address in the spam was bogus.  In both cases,
sendmail logged a failed attempt to deliver the bounce message immediately
before it logged the message shown above:

Sep  6 06:59:59 jik2 sendmail[2513]: l81MB8Ms007747:
to=<PennysycophantBonilla>, delay=4+12:48:51, xdelay=00:00:01,
mailer=esmtp, pri=6422021, relay=mail.phpxref.com. [207.210.228.51], dsn=4.0.0,
stat=Deferred: Connection refused by mail.phpxref.com.

In both cases, the file name shown in the log message didn't actually exist in
/var/spool/mqueue after the fact when I checked (I don't know if it existed at
the time the error occurred).

Obviously, I'm not terribly concerned that sendmail failed to send a bounce
message in response to a spam, but I am concerned that this problem could occur
with legitimate as well.

I've been keeping my machine up-to-date with Rawhide and I don't think I've seen
this error before this past week, despite the fact that thousands of email
messages go through my system each week, so I'm suspecting that there's a recent
change that's causing this issue.