Severe Email Delivery Issues
So, we are experiencing horrid email delivery issues to Google, Hotmail & Yahoo.
Our MTA is Postfix, running on a Centos box with Virtualmin/Webmin running too. All emails are DKIM signed and we have valid PTR and SPF records also. I have tested our emails with various DKIM/SPF & SpamAssassin checking tools and the results are as follows (using Port25's tool):
SPF check: pass DKIM check: pass Sender-ID check: pass SpamAssassin check: ham
I have also checked and it appears that Gmail can see that the emails are signed & SPF works etc.. I have checked to see if our IP appears on any blacklists and the results are all clean, but still we cannot get delivery to most email services. Errors received in the mail log as as per the following (email addresses removed for privacy):
to=<firstname.lastname@example.org>, relay=mx-eu.mail.am0.yahoodns.net[184.108.40.206]:25, delay=59400, delays=59400/0.06/0.06/0.01, dsn=4.7.1, status=deferred (host mx-eu.mail.am0.yahoodns.net[220.127.116.11] said: 421 4.7.1 [TS03] All messages from 18.104.22.168 will be permanently deferred; Retrying will NOT succeed. See http://postmaster.yahoo.com/421-ts03.html (in reply to MAIL FROM command))
to=<email@example.com>, relay=mx3.hotmail.com[22.214.171.124]:25, delay=1.2, delays=0.08/0/0.49/0.67, dsn=2.0.0, status=sent (250 <firstname.lastname@example.org> Queued mail for delivery)
None of the emails are delivered successfully. I have been in touch with both Yahoo and Hotmail via their respective forms and have signed up to Hotmail's SNDS & JMRP and Yahoo's JMRP. Neither of the JMRP's have sent any reported emails through and SNDS says our IP is normal and that we're not blocked.
Has anyone experienced similar before? I would massively appreciate ideas/thoughts/feedback