Thank you for the reply Thomas,

Being able to include sender:, reply to: and errors-to: would be handy in my 

However, in this case the local domain was not in any of the from: fields 
whatsoever. By using<>, this hits 
a stupid bug in Outlook where in some places it will only display 
n...@recipientdomain.tld<mailto:n...@recipientdomain.tld>. The is 
completely fictional and varies from message to message. I thought this would 
not be caught by nospoofing because that would only match if the RHS ended in 
the entry from localdomains.

All the best,

From: Thomas Eckardt <>
Sent: 13 April 2018 16:55
To: ASSP development mailing list <>
Subject: Re: [Assp-test] Multiple From headers/regex based on localdomains


'DoNoSpoofing4From' should do it - but it is'nt. Only the first 'From:' address 
is currently checked and this will not prevent this attack.
But it is possible to include 'sender: , reply-to: and errors-to:' in to this 
check - which would catch this mails.

What do you think?


Von:        "Colin Waring" 
An:        "ASSP development mailing list" 
Datum:        13.04.2018 17:17
Betreff:        [Assp-test] Multiple From headers/regex based on localdomains


I’ve a couple of fun ones at the moment. Basically I’m getting reports of 
phishing emails that get past everything.

The headers are like this:

Reply-to: Sender Name 

To: recipi...@recipientdomain.tld<mailto:recipi...@recipientdomain.tld>

From: Sender Name <f...@domain.tld<mailto:f...@domain.tld>>

From: Sender Name <f...@domain2.tld<mailto:f...@domain2.tld>>

From: Sender Name 

These bypass no spoofing as none of the from/SMTP header domains are actually 
the recipient domain. Annoyingly, Outlook chooses the Reply-to address to 
display so it appears almost legitimate.

I’m aware that the RFCs allow multiple from headers, though I can’t see of any 
legitimate reason for this so I was considering blocking or increasing spam 
score based on this – is this possible with ASSP at the moment or not?

The second thing I was looking at doing was coming up with a regex. 
Essentially, all recipient domains are in localdomains.txt so I’d want a regex 
that would take all lines from localdomains. If the reply to or smtp from 
address is a line from localdomains with anything else after it, then bin it. I 
accept that there may in some extremely obscure cases be a clash with a 
legitimate domain but do not believe that to be likely. I’ll have a look next 
week as to if I can figure out a way to do it but if there’s something obvious 
that you could let me know that’d be great.

All the best,


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