Email receiving but not sending on some devices, not others Sept 2022

[CatSM]

On my iMac running Catalina and using apple mail (BTW, I have been a shaw internet customer using a Mac since 2005 using apple mail the entire time). I am able to receive email but not send - it cannot connect to the SMTP server. This problem just began a few days ago. My older computer running Mojave works fine and all of the other Apple devices work.  

The Mac community recommended downloading and trying different email clients to see if I could get it working and to narrow down the problem. Outlook and Spark work but other clients such as Edison did not connect to the outgoing server either. This issue is with both pop and IMAP.   Any help with this would be appreciated.

[mdk]

@CatSM -- with any Internet connection (Shaw, Rogers, Bell, Telus) you should be able to "authenticate" to Shaw's mail-server, to download your messages.  However, if your device is not connected to Shaw (through your cable-modem) or it is a smart-phone using cellular data, then you need the correct configuration on your E-mail client to authenticate to Shaw's SMTP-server, because Shaw's SMTP-server is primarly configured to be a SMTP-server only for Shaw-connected devices.

[CatSM]

My computer IS connected to a Shaw cable modem through wifi and has been for years.