On 4/14/19 12:04 PM, Sébastien Riccio wrote: > Hello mailop, > > We're a "small" internet service provider in Switzerland and are running mail > services for our customers. > > Since a long time, customers are complaining that the mail they send are > always getting to junk folder at outlook.com (no issues with gmail for > example). > > We give a lot of time to keep our mail servers reputation as good as possible > and I think we're quite doing a good job at it. > > - We're not in any blacklist > - Our senderscore is at the moment 98% > - Talos intelligence mail reputation is good. > - Our customer domains have spf records, dkim, dmarc configured and checked > with no errors. > - On the Microsoft SNDS we have no apparent issue and the complaint rate is > always <0.1% > https://i.imgur.com/rBJXlV6.png >
I have seen this same problem for the past 20+ years of doing enterprise email support back to Exchange and continuing with Office 365 and outlooks.com. The Junk Email folder logic inside Outlook/Forefront Online Protection/Exchange Online Protection (whatever Microsoft is calling this week) is very inconsistent in it's classification/sorting. From what I can tell, it doesn't seem to be based on any industry standards that you mentioned like SPF, DKIM, DMARC, RBLs, SenderScore reputation, Cloudmark scoring, etc. or even the sending domain or body content. When people ask me this question, I recommend they turn off the Junk Email feature. I know this doesn't help from the sending perspective since it's impractical to get all recipients to disable this feature in Outlook.com or Office 365. Somehow our mail relay IPs have been able to deliver to Office 365 and Outlook.com/Hotmail.com reiably and consistently. Here's what I have done over the years: - Sign up for as many feedback loops as possible (Yahoo, AOL, Comcast, etc.). - Make sure FCrDNS is setup perfectly for your outbound mail server IPs with a one-to-one A record and PTR record matching the EHLO. Example: http://multirbl.valli.org/lookup/96.4.1.10.html - Make sure your outbound mail relays have their own SPF record for bounce messages. Example: https://dmarcian.com/spf-survey/?domain=smtp2n.ena.net - Filter outbound mail with some deep header inspection to catch bad senders before they damage your mail server's reputation - Enable compromised account detection to discard spam from single senders quickly based on unusual activity - Try rate limiting your outbound mail to outlook.com. Maybe MS considers us smaller senders as suspicious after X messages per day per IP. -- David Jones _______________________________________________ mailop mailing list mailop@mailop.org https://chilli.nosignal.org/cgi-bin/mailman/listinfo/mailop
