I've been through a mile of pain to finally end up back on Thunderbird, for exactly this use case.

This is what has finally ended my years of Microsoft Office use: Outlook will not let you keep your primary address out of smtp headers. No way, no how.

But, your mail might bounce without proper sfp setup. (preventing random from like in the good old days ([email protected]) is pretty much the raison d'être for sfp... For better or worse).

That's not relevant for the discussion in this thread where we already assume you have a custom domain with catchall inbox setup. The custom From is still needed to be able to actually send from any address on that domain.

Yes, and part of that setup is proper sfp setup? Eg allow sending from Gmail with a from on your domain?

I don't see how it's specific to sending from thunderbird. It's a general issue if you want to use a domain for mailing.

It's not spesific to the mua, no. But as thread starter (ed: first responder) said:

> Word of advice for anybody doing this: make sure you have a way to SEND email using one of your aliased addresses

So a) you need a mua like thunderbird that let's you set FROM header - and b) your domain need to be setup to allow your smtp server(s) to send from your domain (sfp).

It's worth noting that many recipients will use SPF and DMARC to avoid accepting "forged" email like this -- spammers make very heavy use of the historical lack of authorisation for sending mail as if from a particular address.

The context of this thread is having a domain with a catchall inbox and that domain already having all the necessary DNS stuff is assumed.

The custom From is just a way to send from any address for that catchall, I was not suggesting to use it to send from abitrary addresses, which would be quite pointless since you then wouldn't get the replies.

The context is also using a third-party service for the catchall, which is less likely to have suitable records set up for sending from.