First, my email is tied to my ISP .

As its affecting multiple different machines and a variety of email clients, with a similar SMTP-based connection issues, it stands to reason that the problem is due to an ISP server-side change that they have initiated.

If they have told you to connect SMTP using port 587, then ensure the same connection is checked/enabled for TLS/SSL security as well.

In reply to a post by jchamier:

TLS 1.2 is recommended.

Indeed, TLS protocol compatibility issues seem a prime suspect, although from the information provided the OP has problems with Thunderbird too.

Port 587 STARTTLS seems to be the isp's preferred method.

Looks as if they still support SMTP over TCP port 25 without encryption, or over port 587 with encryption. TLS 1.2 is recommended.

Some very old info:
https://answers.microsoft.com/en-us/outlook_com/foru...

~Perhaps they've made the change on the mail servers but neglected to update the FAQ...

Does the OP's version of Outlook actually support the newer version of TLS 1.2? Not sure. as I haven't used Outlook in over a decade or more

Well, I am so grateful for all the suggestions but not getting anywhere and even Idnet are not answering the phone and can't email them!!! Will go and lie down in a darkened room for a while.....................

Andrew - come out of the darkened room, its lovely and sunny out

Is your version of Thunderbird v27 or older?

In reply to a post by Pheasant:

Does the OP's version of Outlook actually support the newer version of TLS 1.2?

Outlook 2003 predates TLS 1.2 by several years, and it was not backported to Outlook 2003 as far as I know.

In reply to a post by Pheasant:

Andrew - come out of the darkened room, its lovely and sunny out

Is your version of Thunderbird v27 or older?

Version 91.10.0 apparently and up to date.


It's raining here!

In reply to a post by Oliver341:

In reply to a post by Pheasant:

Does the OP's version of Outlook actually support the newer version of TLS 1.2?

Outlook 2003 predates TLS 1.2 by several years, and it was not backported to Outlook 2003 as far as I know.

So how is it that it stopped working three days ago?!!

I will endeavour to update my version and see what happens.

Ah shame about the weather, quite balmy here.

Other than the port number for SMTP - are you using the current server names in the mail client settings, as per the guide here?

In Thunderbird have you enabled STARTTLS in connection security for the outgoing server?

Try the free version of eM Client: https://www.emclient.com/download