I ran into a problem while maintaining MARC, the open source mailing list archive with some very large user groups. Especially the linux-kernel archive, with almost 10.000 messages per month.
Some of those messages stopped getting parsed, with these errors in the logs.
Mar 23 21:51:42 ma postfix/local[14420]: 3874942816: to=<linux-kernel@xxx>, relay=local, delay=0.42, delays=0.41/0/0/0.01, dsn=5.2.2, status=bounced (cannot update mailbox /var/mail/linux-kernel for user linux-kernel. error writing message: File too large) Mar 23 21:51:59 ma postfix/local[14420]: 6288D42816: to=<linux-kernel@xxx>, relay=local, delay=0.33, delays=0.32/0/0/0.01, dsn=5.2.2, status=bounced (cannot update mailbox /var/mail/linux-kernel for user linux-kernel. error writing message: File too large)
This message got triggered when the mailbox reached 50MB in size. This is, in fact, a default limit in Postfix called mailbox_size_limit. Here’s the default:
$ postconf -d | grep mailbox_size_limit mailbox_size_limit = 51200000
In order to increase the limit, edit /etc/postfix/main.cf and increase the size.
$ vim /etc/postfix/main.cf ... mailbox_size_limit = 5120000000
This changes the limit from 50MB to 5.000MB. Now reload Postfix and your new mailbox limit is in effect.
$ service postfix reload
Done.