DMARC, Yahoo and mailing lists

[Andrew Daviel <advax () TRIUMF CA>]

Has anyone had problems with Yahoo email users and mailing lists since 
April, and if so what did you do about it ?

http://blog.threadable.com/how-threadable-solved-the-dmarc-problem

Apparently there's a patch available for mailman, but I haven't tried it yet.


I hadn't been made aware of any mailing list problems here, but now I start 
looking into it with some test accounts, it seems I cannot send a message via 
mailman from a yahoo account to another yahoo account, or from a yahoo account 
to a hotmail account. Not just being filtered as spam, but actually 
getting an SMTP rejection.


When I check, I see that at least the following now have "reject" DMARC 
records:
facebook.com
linkedin.com
paypal.com
yahoo.com
twitter.com

viz. DNS TXT records for xxx.tld, e.g. "host -t txt _dmarc.yahoo.com"
or "dig +short -t txt _dmarc.twitter.com"

This probably has implications for Unix-style mail forwarding, too - 
forwarded linkedin and facebook notifications may fail if the target 
domain implements DMARC filtering.


--
Andrew Daviel, TRIUMF, Canada
Tel. +1 (604) 222-7376  (Pacific Time)