On some machines localhost is defined as something other than 127.0.0.1, and if we mix "127.0.0.1" and "localhost" then some connections won't be to to the address a service is actually running on.
This was the case with DKIM: It was running on "localhost" but Postfix was connecting to it at 127.0.0.1. (https://discourse.mailinabox.email/t/opendkim-is-not-running-port-8891/1188/12.)
I suppose "localhost" could be an alias to an IPv6 address? We don't really want local services binding on IPv6, so use "127.0.0.1" to be explicit and don't use "localhost" to be sure we get an IPv4 address.
Fixes#797
* Add a migration to delete any existing DKIM key so that existing machines get a fresh 2048-bit key. (Sadly we don't support key rotation so the change is immediate.)
* Because the DNS record for a 2048-bit key is so much longer, the way we read OpenDKIM's DNS record text file had to be modified to combine an arbitrary number of TXT record quoted ("...") strings.
* When writing out the TXT record value, the string must be split into quoted ("...") strings with a maximum length of 255 bytes each, per the DNS spec.
* Added a changelog entry.
Currently MiaB creates 1024 bit keys which is seen as a minimum standard
by several providers such as Google who already uses a 2048 bit key.
Increasing the keysize beyond 2048 is an issue as it often goes beyond
supported DNS record sizes.
I added OpenDMARC's milter in fba4d4702e. But this started
setting Authentication-Results headers on outbound mail with failures. Not sure why it
fails at that point, but it shouldn't be set at all. The failure might cause recipients
to junk the mail. See #358.
This commit removes the milter from the SMTP submission (port 587) listener.
