I have recently added a few lines to procmail to move duplicate messages
to a folder named duplicates. Most of the time I don't get an error
message, but sometimes I see this in the log:
procmail: Error while writing to "formail"
my rc file is:
:0 Whc: msgid.lock
| formail -D 8192 /home/chadr/Procmail/msgid.cache
Again, most of the time this works, but sometimes I get the error. There
are no errors in /var/log/messages to indicate a problem on the drive.
I've turned on log details in procmail hoping that will give me a better
idea. This receipe was copied directly from the procmailex man pages.
procmail mailing list