In general, the checks interface with added scoring and quarantining
support was not convenient to use enough. Also it was problematic
to add support for Authentication-Results header field generation.
Per-sender and per-recipient checks were not applied to body.
This is fixed now.
Checks inspecting the message header was able to see header
modifications done by other checks. This could lead to unwanted
side-effects and so now checks can't modify the header directly
and instead can only prepend fields to it by returning them.
Additionally, it allows checks to return values for
Authentication-Results field. Each server handling the message should
add only one field, so it is not possible to implement it using header
prepending.
MsgMetadata.CheckScore is removed, now it is managed internally by
dispatcher code and not exposed where it is not needed.
MsgMetadata.Quarantine is no longer set directly by checks code. Future
refactoring may be remove it altogether as it is discouraged to have
mutable flags in MsgMetadata.
On top of that, tests are added for all new code.
Consider anything with more than 1 argument to be inline definitions.
Combined with previous change it allows writing stuff like
'deliver_to proxy smtp://blah:25'. This looks natural despite
actually using kinda strange (for non-programmers) abstractions
of maddy module framework.
This allows more readable configuration files without additional
explanations in cases where a single module is used for multiple
purposes.
Also cleans up certain problems with modules that rely on block
names having certain semantics (e.g. endpoint modules).
It was quickly hacked in, built on the pile of broken abstractions
and was source of several bugs.
This commit is almost full rewrite of most functions in config.go.
* Drop most of the implicit defaults in favor of explicit configuration
We no longer follow caddy's "zero-configuration" approach. Mail is much
more complex than HTTP and we want to be explicit about things, always.
* Remove commented out directives from maddy.conf
