I'm running 8.8.5 sendmail. I have user who doesn't use the .procmailrc
file, but I still see a username.lock file in /var/spool/mail/username.
When the lock file appears, No mail gets delivered to that user. I've
built sendmail 8.8.5 with macros, incorporating procmail into the
sendmail.cf file. I'm totally desperate for a solution. One user out of 85!
Lots of other things besides procmail use the .lock file mechanism. (And
depending on your system it may be just one of a few that procmail uses.)
Is he using POP to get his mail? Does your popper use the .lock mechanism? Is
there a disk quota that would make that .lock mechanism break?