When I run the command inside the container (as I saw in the Discourse SMTP troubleshooting guide):
openssl s_client -connect foo.mail.protection.outlook.com:25 -starttls smtp
Everything looks normal but instead of a 250 DSN, I see a 250 SMTPUTF8. Then when I try to enter the command EHLO "i am here", nothing happens and I eventually time out:
451 4.7.0 Timeout waiting for client input [YT1PEPF00001E8C.CANPRD01.PROD.OUTLOOK.COM 2024-02-23T17:51:16.770Z 08DC342D15BDD245] read:errno=0