If the server settings you're using are those appearing in the screenshot, then you're using incorrect settings. I don't understand why you're fetching messages from your ISP mailbox and not directly from your own domain. Whatever your reasons, just make sure you configure Tbird using the correct server settings. TPG published insecure settings here https://www.tpg.com.au/support/emailsetting

Use the Manual Config option to setup the account, using the settings given there. If TPG offers secure (SSL/TLS) mail, get the right settings from them.

Thank you for following up, Stans.

The incorrect settings were automatically set by Tbird. Thanks for finding them for me but those mail.tpg setting also do not work on Tbird although they work with Opera Mail - weird. I'm still attempting to get something meaningful from the ISP. I'm not the only TPG user reporting recent interruption to a previously perfectly-performing Tbird/TPG account. Something changed at about the time of the latest Tbird upgrade.

To answer your question, I'm using my ISP mailbox for the redirects as I find it easier to access emails (before it all went haywire, that is) from there, but I'm open to other ideas. ;)

I will report back when I (if I) can get this sorted.

Thanks again.

Correction. Opera Mail does not send from mail.tpg (goes into the Draft folder with no error message) but it does collect. Thunderbird does not collect (no error) nor does it send (see screenshot).

Use the following manual settings in Thunderbird:

Protocol: POP3 Incoming server name: mail.tpg.com.au Port: 110 SSL: None Authentication: Normal Password

SMTP Outgoing server name: mail.tpg.com.au Port: 25 SSL: None Authentication: Normal Password

TPG's settings are not in Thunderbird's database of known email service providers database, so it makes a guess using "common server names". You can't rely on those. Use the official settings given by TPG on their website, or as summarised above. Those settings should work in Thunderbird without any problem assuming all is well on TPG's side.

To answer your question, I'm using my ISP mailbox for the redirects as I find it easier to access emails (before it all went haywire, that is) from there, but I'm open to other ideas. ;)

TPG would be the last email service provider I could think of using, more so when you've got a custom domain and business email, hosted by a much better email provider like Fastmail. 2FA and SSL/TLS are all it would take me to use Fastmail instead of TPG. TPG might as well quit the email business altogether and just focus on whatever else they do best, but that is just my opinion and I digress.

Going by the posts here, it seems there is undocumented secure mail support by TPG, on ports 995 (POP3) and 465 (SMTP), which seems to contradict TPG's support's claim, so you may give those ports a try and set the SSL field to SSL/TLS in Thunderbird. If those work, well and good.

I find fastmail's interface very easy to use and intuitive; I signed up for a 30-day trial to see what it is I might not like about Fastmail. There is a good setup guide for Thunderbird as well, for working directly with your Fastmail-hosted mailbox. My trial Fastmail account is working beautifully with Thunderbird 78 via secure IMAP & SMTP. I'd advice you bypass TPG and just access your Fastmail mailbox directly.

Thank you so much Stans,

Your reply just arrived immediately after I wrote to Fastmail with the same conclusion. I'm getting excellent help from Marin there. I've finally got Tbird working again at TPG but like you am asking FM how to get them to replace TPG.

I've been with fastmail for over 10 years - long before brandgrafix and I love their service so I concur with everything you say.

Thank you so much for your advice and attention and for going to so much trouble. It is very much appreciated. I think I'm good from here on ;)

am asking FM how to get them to replace TPG

Why would they want to do that?

Sorry, I wasn't clear. I meant I had come to the exact conclusion you were recommending; not a company replacement but moving my forwarding away from TPG and back to Fastmail, as long as I can get a sep[arate inbox for brandgrafix that is accessible by Poppeeper so that I can tell brandgrafix emails are not the same as my fastmail emails which are serving different purposes.

Fastmail is giving me great service so I am confident it will be done.

I thank you for all your help and suggestions.

You will need to add a user to your Fastmail account (each user gets a separate login and inbox), then you can use that account's inbox to separate your Fastmail and brandgrafix emails, or you could save the cost of adding a new Fastmail user and create a new email account in your brandgrafix domain hosting account and use that for forwarded brandgrafix emails, if storage space is not a problem. You could also just sign up for a free Outlook.com account and use that, that is IF you trust big brother Microsoft with your brandgrafix emails.

I'm sticking with Fastmail, Stans. That IF is not an if for me ;)

Good choice. That settles it then.