exim-4.77 stopped delivering mail when my inbox reached 2148124249 bytes. From /var/log/mail.log: ... R=localuser T=local_delivery defer (27): File too large: error while writing to /var/mail/chkno/inbox ... R=localuser T=local_delivery defer (75): Value too large for defined data type: attempting to stat mailbox /var/mail/chkno/inbox Mail was lost. :(
What filesystem is this? The 2GiB barrier, sounds a lot like you hit a limitation that Exim can't do much about. emerge --info might be nice here also.