Nothing has changed in the last 4 weeks. Still cannot send email using Thunderbird since the Telstra network upgrade.
The modem is the same as it was a month ago and has not had any changes made before or since.
Both computers that use Thunderbird had not had any changes made to them before the issues arose and both computers were able to send email before the Telstra upgrade. I have spent hours on the phone to Telstra and Optus (once you get through their ridiculous IVR systems which seem to be intent on dissuading customers from talking to anyone). Both organisations say everything is fine at their ends.
According to Optus, the outgoing SMTP email server is mail.optusnet.com.au and it uses port 25. Thunderbird now cannot connect on that port and I believe that is because Telstra is probably blocking it (although the person I spoke to at Telstra said they have not received any communication about blocking port 25 and there are no technical people they can put me through to to discuss it).
I can't use Telstra's SMTP email server as I am not using a bigpond email address - I have an optusnet email address and it was working fine until about 4 weeks ago when Telstra upgraded something.