[Question] Email flow when using with milter

Eoin Kim Eoin.Kim at rcst.com.au
Tue Jun 26 21:29:59 UTC 2018

Really appreciate it Mark. I misunderstood few things since the MailScanner interface shows the result of SPF and DKIM check. I thought they are done by MailScanner. Okay, so as long as the original sender can receive some kinds of notification message, I might try to apply a milter. I am really sorry for bothering all of you but more questions.

  1.  I can see there are lots of milter add-ons for Postfix. Are they all doing different jobs? Like you said before, I don't want to deploy redundant milters.
  2.  Do you have any suggestions?

Thanks very much.


-----Original Message-----
From: MailScanner <mailscanner-bounces+eoin.kim=rcst.com.au at lists.mailscanner.info> On Behalf Of Mark Sapiro
Sent: Wednesday, 27 June 2018 12:44 AM
To: mailscanner at lists.mailscanner.info
Subject: Re: [Question] Email flow when using with milter

On 6/26/18 12:24 AM, Eoin Kim wrote:

> Thanks Mark,


> So, if I interpret your comment in my own way, if the milter rejects the message, no one (both sender and receiver) will know about what happened to the message. Am I following you? If so, that wouldn't be a pleasant situation for me.

The sending MTA will receive an SMTP 5xx status with a reason provided

by the milter. What happens then depends on how the mail was sent, but

the original sender should be notified somehow. The difference is any

delivery status notification which may be backscatter to a spoofed

sender will come from the sending MTA or upstream and not from your

server. This is a good thing.

> Are there any features similar to milters I can use in MailScanner? I believe, SPF, DKIM, RBL check is possible with it, correct? Thanks again.

The one big downside of MailScanner is your server has already accepted

the mail before MailScanner sees it. Thus, any backscatter generated by

a MailScanner notice comes from you. MailScanner can check RBLs.

Generally SPF and DKIM validation are done by the incoming MTA which

generates results headers that are checked by SpamAssassin running by


MailScanner does support custom functions as a hook to your own code,

but this is somewhat limited and doesn't support a 'milter' interface.


Mark Sapiro <mark at msapiro.net<mailto:mark at msapiro.net>>        The highway is for gamblers,

San Francisco Bay Area, California    better use your sense - B. Dylan


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