How else would that work, though? Thunderbird doesn't know what SMTP server and credentials to use without you telling it.

It knows the domain already and SMTP credentials are already saved.

I’ve already set creds for abc@domain.tld, xyz@domain.tld and pr course as usual I can reply, send new emails from these addresses.

But I should also be able to send emails/reply from pqrs/dfg/john/tom/ram/bond/bill/etc@domain.tld. Of course reply will be automatic but sending new email might just require changing the from field.

It can have a setting that “if a from address identified isn’t already added as an identity, it should use the SMTP creds of matching domain”. It won’t work for something like Gmail, Outlook.com (I mean one anyway can’t have catch-all on these domains) but would work great for personal emails.

This is what I meant.

Because without such a feature - catchall feature is often rendered very limited. Even iCloud+ supports replying - id you’ve to send a fresh mail from a catchall/disposable (or service/provider/business specific) email address you’re out of luck.

My thunderbird has an option for “modify from …” which lets me write whatever I want. On mobile, can’t check exact text. I do remember I had to reggae a switch in the preferences to make that option appear, don’t remember which one - have been using it for years.

Just checked, it's called "Customize From Address ..."

Cool! Thank you! Works great. Just have to remember to get rid of my signature as it has all my personal contact info lol

Thunderbird has a mobile app as well? The website says it doesn’t.

I was away from my laptop on mobile writing the message, so I couldn’t check what the option was called on my laptop….

It used to work fine with an extension called Virtual Identity. That no longer works (hasn't been updated in a long time, and I'm not sure if it could be made to work again).

No it doesn't, you can use a wildcard.