Mail size is larger than the maximum size allowed by server configuration

[tilllt]

Recently i didnt receive some messages with my Getmail / Dovecot / Postfix setup, without noticing at firrst, because the Mail just was skipped. Later i found out that Dovecot has problems storing large Messages into the mailbox.

Its possible to configure dovecot size limits, but per Dovecot defaults they are not set. Does DMS override those defaults and actually defines message size limits for dovecot?

2025-03-30T09:43:33.803089+02:00 mail dovecot: lda(mail@mail.example.de): Error: sieve: msgid=<xxxxx@mail.gmail.com>: failed to store into mailbox 'INBOX': Mail size is larger than the maximum size allowed by server configuration                                                       
2025-03-30T09:43:33.803216+02:00 mail dovecot: ldamail@mail.example.de): Error: sieve: Execution of script /usr/lib/dovecot/sieve-global/after/spam_to_junk.sieve failed with unsuccessful implicit keep         
2025-03-30T09:43:33.809912+02:00 mail getmail: Delivery error (command rspamc 3987537 error (75, ))                     
2025-03-30T09:43:33.809931+02:00 mail getmail: msg 416/583 (13163082 bytes) msgid 12334/1234from <xyz@gmail.com>

[polarathene]

You might have to investigate this yourself to find what setting is affecting it. Dovecot Quotas are enabled by default, and we do have this snippet applied:

docker-mailserver/target/scripts/startup/setup.d/dovecot.sh

Lines 168 to 182 in 23bb1c8

	local MESSAGE_SIZE_LIMIT_MB=$((POSTFIX_MESSAGE_SIZE_LIMIT / 1000000))
	local MAILBOX_LIMIT_MB=$((POSTFIX_MAILBOX_SIZE_LIMIT / 1000000))
	sedfile -i \
	"s|quota_max_mail_size =.*|quota_max_mail_size = ${MESSAGE_SIZE_LIMIT_MB}$([[ ${MESSAGE_SIZE_LIMIT_MB} -eq 0 ]] && echo "" || echo "M")|g" \
	/etc/dovecot/conf.d/90-quota.conf
	sedfile -i \
	"s|quota_rule = \*:storage=.*|quota_rule = *:storage=${MAILBOX_LIMIT_MB}$([[ ${MAILBOX_LIMIT_MB} -eq 0 ]] && echo "" || echo "M")|g" \
	/etc/dovecot/conf.d/90-quota.conf
	if [[ -d /tmp/docker-mailserver ]] && [[ ! -f /tmp/docker-mailserver/dovecot-quotas.cf ]]; then
	_log 'trace' "'/tmp/docker-mailserver/dovecot-quotas.cf' is not provided. Using default quotas."
	: >/tmp/docker-mailserver/dovecot-quotas.cf
	fi

That is used for Postfix to limit too:

docker-mailserver/target/scripts/startup/setup.d/postfix.sh

Lines 55 to 62 in 23bb1c8

	__postfix__log 'trace' "Configuring message size limit to '${POSTFIX_MESSAGE_SIZE_LIMIT}'"
	postconf "message_size_limit = ${POSTFIX_MESSAGE_SIZE_LIMIT}"
	__postfix__log 'trace' "Configuring mailbox size limit to '${POSTFIX_MAILBOX_SIZE_LIMIT}'"
	postconf "mailbox_size_limit = ${POSTFIX_MAILBOX_SIZE_LIMIT}"
	__postfix__log 'trace' "Configuring virtual mailbox size limit to '${POSTFIX_MAILBOX_SIZE_LIMIT}'"
	postconf "virtual_mailbox_limit = ${POSTFIX_MAILBOX_SIZE_LIMIT}"

Defaults in DMS for those two ENV:

docker-mailserver/target/scripts/startup/variables-stack.sh

Lines 138 to 139 in 23bb1c8

	VARS[POSTFIX_MAILBOX_SIZE_LIMIT]="${POSTFIX_MAILBOX_SIZE_LIMIT:=0}"
	VARS[POSTFIX_MESSAGE_SIZE_LIMIT]="${POSTFIX_MESSAGE_SIZE_LIMIT:=10240000}" # ~10 MB

[tilllt]

Thanks for the pointers.

Dovecot docs says the default max mail size is unlimited:

https://doc.dovecot.org/main/core/plugins/quota.html

Just a suggestion: Gmail allows its users to send 25MB per Mail, so maybe this should be used as default?

And: if a mail that's too big arrives, in a Getmail6 setup, it retrieves the mail but then silently fails processing it.

Maybe there is a global variable that could be set that would "sync" all components (getmail, dovecot, postfix) to handle the same incoming max mail size... If not, getmail6 retrieves it but dovecot doesn't process it so it silently disappears in DMS.

[polarathene]

Yeah I believe there are some past discussions about that concern. I can't recall why no change happened, it may have just lacked someone opening a PR to make the change.

Would likely be delayed until v16 release as technically a breaking change.

I can't comment much on the Getmail6 concern, it may have a setting that could alter that failure behaviour but that's a good point too :)

As for global variable, I think that's how the two message/mailbox limits above are being treated already between Postfix and Dovecot? (Getmail6 arrived much later)

[tilllt]

Maybe if there are future changes to this logic, it would also be worth considering to rename

POSTFIX_MESSAGE_SIZE_LIMIT

to something that implies that this is used throughout all the tools in DMS, not only in Postfix.

[polarathene]

You are probably right, that is a setting that was added to DMS before I became a maintainer years ago. Chances are it may have existed before DMS even had Dovecot 🤷‍♂️ (that would be prior to DMS v2)

The review process is more thorough these days, but the project does have a fair bit of legacy contributions that still need to be cleaned up, it's just a lack of any contributor having time to properly tackle these as we often have higher priority items that we allocate our available time to on the project.

I'll add it to my TODO list (EDIT: done), so it should get taken care of eventually. I've got some larger tasks assigned to me that I need to resolve before I take on any more myself, so I can't say when this will be handled.