[Question] Email flow when using with milter

[Mark Sapiro]

On 6/25/18 10:13 PM, Eoin Kim wrote:
> 
> I’d like to ask a question regarding email flow on the MailScanner. So,
> if I understood correctly, the below is what’s happening (briefly):
> 
>  1. Server receives an email and goes to hold queue (/^Received:/ HOLD).
>  2. MailScanner works on the message with SpamAssassin and ClamAV.
>     Depending on the result, message can go either incoming queue or
>     quarantine.
>  3. Postfix sends out the message from incoming queue.


Correct, but MailScanner does more than just ClamAV and Spamassassin.


> Am I following it? Please correct me if I am wrong. If I am correct, I’d
> like to ask more questions. I found there are few milters and I am
> particularly interested in spamass-milter and clamav-milter. Now, the
> questions are:
> 
>  1. The very first question is, I remember MailScanner doesn’t have
>     built-in milter, correct?

Yes.


>  2. Is having multiple milters on the system helpful?

If they do what you want and don't duplicate effort.


>  3. Are they all before-queue milters? If so, what is the email flow?
>     Just more operations in the hold queue?

They operate before the hold queue during incoming SMTP. The plus side
is they can reject the mail at incoming SMTP which avoids the
possibility of sending notices to a spoofed sender. The minus is if a
milter rejects the mail, No one, including MailScanner sees it and no
MailScanner rules about forwarding, quarantining, etc. can be done.

-- 
Mark Sapiro <mark at msapiro.net>        The highway is for gamblers,
San Francisco Bay Area, California    better use your sense - B. Dylan