49MB mailbox size limit (Postfix & procmail)

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.

20 thoughts on “49MB mailbox size limit (Postfix & procmail)”

  1. 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…

  2. 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

  3. 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.


  4. I’m so glad there are still people who unselfish and generously help others.

    Thank you very much.


  5. Hey,

    Thanks a lot.. Faced the same problem this morning, and was wondering what was wrong with procmail. on googling found this post, and it helped.

  6. Thank you… this is this, what the Internet is about… just share with the piece of information and for sure someone will find it useful.

  7. Thanks! This problem had been bugging me for a while, I was assuming it was some bizarre procmail limitation and searched the mailing lists in vain. Every few months my spam mbox overflows 50 Mb and then it would deliver them all as if they hadn’t matched the spam rules which was totally obnoxious.

  8. Saved my butt. I’ve inherited an ancient mail system that runs procmail, system-wide. LOVE YOU MEEEN! :)

  9. Brilliant!

    I’ve just moved to a new email server, and procmail suddenly started to bounce emails back to the sender.

    All documentation & support suggested that the inbox had wrong permissions – totally wrong, it was the fact that the inbox had reached 49MB and so postfix (when procmail called it) was denying adding any more email to the inbox.

    Sorted now – thanks to this post!
    Dean Richardson

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