This is really impressive. There are several failed attempts at mailserver setups in the Docker registry.
I understand the need to have charge for more featureful setups. However, the free version is useless without DKIM and SPF support - outgoing mail will end up in spam folders.
Thanks! SPF is matter of DNS only. DKIM can be added to domain through command line even in free version. (but you are right, i will release DKIM to free version also)