Office 365 - The SMTP server does not support the STARTTLS extension.

[ksanch]

Hi, i'm trying to configure the mail option. I'm getting the following error:

The SMTP server does not support the STARTTLS extension.

I get this error with 3CX SMTP server, Outlook.com, Office 365 and Gmail. I looked for it on the forums but no answers worked for me.

3CX version: 16.0.676
3CX licence: Enterprise Annual
3CX Debian 9.5
Firewall Checker passed

 

[Alphabetic]

If you select type: Office365 and put in your 365 credentials it works fine..

are you trying to use custom?

 

[ksanch]

Hi kieferschild, Thanks for your answer. Yes I tried my Office 365 credentials. And of course I tested Outlook.com with my Outlook.com credentials, Gmail with my Gmail account etc. but no success.

 

[ksanch]

I managed to get it to work, bypassing our SMTP proxy

 

[Alphabetic]

Does it work with 3CX SMTP?

Do you have an active license?

Try refreshing your license details.

 

[Alphabetic]

I managed to get it to work, bypassing our SMTP proxy

What do you mean?

 

[cobaltit]

What do you mean?

What he means is it had nothing to do with 3CX. He has a edge device configured to proxy SMTP connections that was interfering with authentication.

 

[ksanch]

What he means is it had nothing to do with 3CX. He has a edge device configured to proxy SMTP connections that was interfering with authentication.

Exactly. First I saw allowed packet on my Firewall that let me guess it wasn't a Firewall problem. But after all the diag on 3CX-side, I by-passed all filtering on my Firewall for 3CX and it worked. Thanks for your time and sorry for inconvenience.