outlook 365 on windows cannot connect to macos server 5.4

#OUTLOOK 365 ON WINDOWS CANNOT CONNECT TO MACOS SERVER 5.4 INSTALL#

No typo’s allowed in telnet, so type carefully.

Type the following to send the email by command line.

You are now connected to Exchange Online Protection and you should get a 220 response.

This will send an email to a fake address at Microsoft, but will hit the TLS error before the message is rejected

#OUTLOOK 365 ON WINDOWS CANNOT CONNECT TO MACOS SERVER 5.4 INSTALL#

Install the Telnet Client feature on your Exchange Server that will be your source server for hybrid or connectivity to EOP for outbound email.If you are on the blocklist then you will get back the delisting email and you can process that whilst setting up the connectors to Office 365 and so by the time you are ready to test, you are off the blocklist! To send a test email over Telnet Therefore my recommendation when setting up Exchange Online Hybrid or stand alone EOP is to send an email over plain text to EOP before you configure your service.

So now you have an NDR with the answer to the problem in, you can fix it! It takes 1 to 2 hours to get delisted from when Microsoft process your email – so they say it takes 48 hours end to end. The NDR for the rejection will tell you to email Microsoft’s delisting service. If you change your connector (temporarily) to allow opportunistic TLS or no TLS at all then your emails will leave the queue – but will be rejected by the Microsoft servers. The reason why you are not getting STARTTLS offered is that your connecting IP address is on the Microsoft block list.

If you are not configuring hybrid or EOP standalone and need to send an email to someone on Office 365 then this is not an issue, because Exchange Server does not require TLS for normal email communication and so the lack of a STARTTLS verb means your email is sent in clear text. Communication between your on-premises servers and Microsoft for hybrid or EOP configurations requires TLS and if you cannot start TLS then your email will queue. STARTTLS is the SMTP verb needed to begin a secure and encrypted session using TLS. If you turn on protocol logging you get this error in the log “Connector is configured to send mail only over TLS connections and remote doesn’t support TLS” and if you look at the SMTP protocol verbs that are recorded in the log you see that Microsoft’s servers do not offer STARTTLS as a verb. You set up an Exchange Online Hybrid or Exchange Online Protection (EOP) stand alone service and follow all the instructions for the creating of the connectors needed, only to find that your emails queue in your Exchange Server.

Outlook 365 on windows cannot connect to macos server 5.4