+1, and while you SHOULD try to block before DATA when you can, to
reduce loads on servers, and not tie up the SMTP connections any longer
than you need, for rules bases on content, it is perfectly well to send
a 5XX after data, and while there may be still some 'broken' MTA's and
clients that don't properly wait for the response code after DATA, that
isn't your problem..
The only complexity comes from when multiple recipients have different
policies for acceptance based on DATA content. Which is why many
systems still do content filtering AFTER acceptance.
There ARE ways to address it in-stream, and there ARE now methods to
return a variable acceptance after DATA, and there are resource
intensive DATA handlers that are best used out of band (eg, after
acceptance) but in general, the more you can stop inband, the better it
is and less potential back scatter.
But yeah.. this thread doesn't really belong on the dovecot list, so
'nuff said ;)
On 2020-06-11 7:43 p.m., Adi Pircalabu wrote:
Rejecting or deferring after DATA is perfectly fine these days. If the
sending MTA, acting as a client in the SMTP conversation, doesn't behave
properly to 5xx after DATA, it's not the recipient's MTA problem, the
sender is broken and there's nothing the receiving MTA can do about it.
Make it their problem, not yours.
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