Here for future reference more than anything else, and to help anyone who’s Googling for this.
I have my email delivered to a box at home running Postfix, and stored by procmail into mbox mailboxes.
I was finding that, whenever a mailbox file reached about 49MB, procmail would no longer deliver mail into that mailbox, instead dumping it into my main system mailbox.
A look at procmail’s logs would reveal:
procmail: Error while writing to "lists/cpan-testers"
procmail: Truncated file to former size
And sure enough, the file was 49MB:
[davidp@supernova:~/INBOX/lists]$ ls -lh cpan-testers
-rw——- 1 davidp users 49M 2007-07-06 16:42 cpan-testers
[davidp@supernova:~/INBOX/lists]$ ls -l cpan-testers
-rw——- 1 davidp users 51198081 2007-07-06 16:42 cpan-testers
After a bit of Googling, I found that this isn’t due to procmail but due to Postfix’s mailbox_size_limit setting. This limit is enforced via UNIX process limits, hence will apply to procmail or whatever the local delivery agent is.
Checking the default value shows:
[root@supernova:]# postconf -d mailbox_size_limit
mailbox_size_limit = 51200000
Okay… there’s the problem.
Changing it to a stupidly high value:
[root@supernova:]# postconf -ev mailbox_size_limit=99999999999999
Problem solved 
I found the details I needed at: http://www.security-express.com/archives/postfix/2003-02/2131.html
Hope this helps somebody.
Wow - I’ve been looking to fix this problem (and find the source) forever… thanks for the solution.
Hardest part was finding something in some logs somewhere so I could perform a helpful Google search. Finally stumbled on the procmail logs…
@TheCase:
Glad it was of use to you, and thanks for taking the time to leave a comment
Made my day as well. Thank you for posting this!
I, too, have been trying to figure this out for ages. Thanks!
It might be worth noting that the -d flag for postconf displays the *default* value always. After changing the setting, if you want to see the currently used setting, you need to using the -n flag instead:
postconf -n mailbox_size_limit
Thank you so much!
Thanks for the page — finding it saved me considerable troubleshooting time on my similar mail setup.
BTW, you can also set mailbox_size_limit to 0, meaning no limit.
Jason.
@Jason:
Glad it was useful to you! Thanks for the comment, and for the hint on setting mailbox_size_limit to zero too!
Many thanks for your help - saved me ages with this tip!
Cheers,
John
good job.
really helped me out.
thanks
uli