<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40"><head><meta http-equiv=Content-Type content="text/html; charset=us-ascii"><meta name=Generator content="Microsoft Word 15 (filtered medium)"><style><!--
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</o:shapelayout></xml><![endif]--></head><body bgcolor=white lang=EN-US link="#0563C1" vlink="#954F72"><div class=WordSection1><p class=MsoNormal>Before looking at technical fixes, I would first ask if I have mail customers whose credentials have been compromises and are being used to send spam. This will get your server IP blacklisted for sending spam. Are you sure the webpage they are sending you to via the SMTP error code isn’t helpful? I’ve seen some that tell you exactly why they are refusing mail from you.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>I suspect that SPF, DKIM and DMARC will be of little to no use in solving this problem.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>You could also check your mailserver IP address for blacklists at a site like <a href="https://mxtoolbox.com/blacklists.aspx">https://mxtoolbox.com/blacklists.aspx</a><o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><div><div style='border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0in 0in 0in'><p class=MsoNormal><b>From:</b> Blueonyx <blueonyx-bounces@mail.blueonyx.it> <b>On Behalf Of </b>Chuck Tetlow<br><b>Sent:</b> Wednesday, June 3, 2020 5:12 PM<br><b>To:</b> BlueOnyx Mail List <blueonyx@blueonyx.it><br><b>Subject:</b> [BlueOnyx:23933] Recent problems with mail delivery to some domains<o:p></o:p></p></div></div><p class=MsoNormal><o:p> </o:p></p><div><p class=MsoNormal>Hello BlueOnyx experts,<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>Has anyone suddenly had problems delivering email to some domains - mostly Hotmail, Outlook, and other Microsoft domains? Over the last couple of weeks - I find that I suddenly can't send email to Hotmail. It bounces back every time with a logged "service unavailable". And the bounce error message leads to a webpage with a very vague explanation - and essentially no way to fix it.<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>I'm also beginning to get multiple inquiries from my customers - when their users can't send mail to M$ domains. So I've got to find a resolution. <o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>I've checked multiple sources, and neither the domain or the IP address is blacklisted. I've checked forward and reverse DNS records - all are correct. I already had a loose SPF record, now have tightened that up - no difference. So I went out to get info on DMARC - and created a DMARC record. Still no help. Every message fails.<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>I considered (briefly) DKIM - but that seems to be a challenging system, which appears to require changes to the MTA. And I just don't know if BlueOnyx supports DKIM, or will allow Sendmail to be modified to use DKIM.<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>So questions: Has anyone else experienced this problem with Hotmail/Outlook/Microsoft.com/etc? And has anyone found a resolution to the problem? I'd love to hear about your fix!<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>Second. Does anyone know if we can implement DKIM in BlueOnyx? I suspect that sooner or later - everyone will HAVE to go to DKIM. As more and more strict SPAM fighting measures are put in place - I believe DKIM will be the ultimate solution to combat spoofing FROM addressing.<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>Thanks everyone. I appreciate any suggestions on fixing this problem. <o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>Chuck<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div></div></body></html>