I cannot send emails from my macbook or my iPhone but can successfully send from the TPG Post Office online. When I hit the send button on the email, I very quickly get an error message saying "Cannot send mail. The sender address was invalid". I do occasionally use a vpn on my Macbook but not always, so not sure if that is an issue? Can't see how it would be as I don't use it on my phone. I have tried changing my password, changing the outgoing port from 25 to 587 but nothing works on either device. Any advice anyone??
Not sure I understand what you mean but...
On phone: In the smtp settings there is only host name and username. there is an email address as username for the incoming mail server and pop account info.
On Mac: The username is my email address in both ingoing and outgoing.
I have all those details in already (and have for years) and both Mac Mail app and the iPhone Mail app have verified the settings. Other than changing my password and testing a different port number (after error to try and fix this problem), I had not made any changes to my account set up on either device prior to getting this error.