Hi Gang I was just able to reproduce a strange issue with an Outlook customer.
Receiving end is Postfix with an Let's encrypt wildcard cert. As far the cert looks valid, the chain looks ok. When the outlook customer is sending an email I see this in the logs: 2026-02-20T15:19:39.867675+01:00 mail postfix/smtpd[115462]: connect from mail-westeuropeazlp170110003.outbound.protection.outlook.com[2a01:111:f403:c201::3] 2026-02-20T15:19:40.034763+01:00 mail postfix/smtpd[115462]: disconnect from mail-westeuropeazlp170110003.outbound.protection.outlook.com[2a01:111:f403:c201::3] ehlo=1 starttls=1 quit=1 commands=3 2026-02-20T15:19:40.065412+01:00 mail postfix/smtpd[115435]: connect from mail-westeuropeazon11021129.outbound.protection.outlook.com[52.101.70.129] 2026-02-20T15:19:40.230800+01:00 mail postfix/smtpd[115435]: disconnect from mail-westeuropeazon11021129.outbound.protection.outlook.com[52.101.70.129] ehlo=1 starttls=1 quit=1 commands=3 2026-02-20T15:19:42.145161+01:00 mail postfix/smtpd[115462]: connect from mail-westus3azlp170100009.outbound.protection.outlook.com[2a01:111:f403:c107::9] 2026-02-20T15:19:42.947705+01:00 mail postfix/smtpd[115462]: disconnect from mail-westus3azlp170100009.outbound.protection.outlook.com[2a01:111:f403:c107::9] ehlo=1 starttls=1 quit=1 commands=3 2026-02-20T15:19:42.993766+01:00 mail postfix/smtpd[115435]: connect from mail-westus3azon11020138.outbound.protection.outlook.com[52.101.201.138] 2026-02-20T15:19:43.835172+01:00 mail postfix/smtpd[115435]: disconnect from mail-westus3azon11020138.outbound.protection.outlook.com[52.101.201.138] ehlo=1 starttls=1 quit=1 commands=3 So obviously outlook just send the three commands: ehlo, startls and quit but never transmit the email. The sender is never getting a notification (issue persists for one week now) about emails not being transmitted. Only emails sent from outlook customer are affected. Anyone else observing that issue and having an idea what the cause could be? -- Mit freundlichen Grüssen -Benoît Panizzon- @ HomeOffice und normal erreichbar -- I m p r o W a r e A G - Leiter Commerce Kunden ______________________________________________________ Zurlindenstrasse 29 Tel +41 61 826 93 00 CH-4133 Pratteln Fax +41 61 826 93 01 Schweiz Web http://www.imp.ch ______________________________________________________ _______________________________________________ mailop mailing list [email protected] https://list.mailop.org/listinfo/mailop
