On Thu, 28 Oct 2021 at 00:15, dovecot@ptld.com wrote:
I think your approach would work, however, if I set up aliases similar to:
@barbaz.mydomain.com -> barbaz@mydomain.com.
I believe I can do that in postfix with some regex magic.
Yes, that would work perfectly without any regex. You just point the catchall alias to the "user". @barbaz.mydomain.com -> barbaz@mydomain.com
I've managed to get this working in postfix - I needed the regex rather than a static map, as I need to extract the unknown subdomain portion but it seems to be working. I have been able to get postfix to save it to a file as well and it seems to work as I expected.
[..]
The purpose of the system is that users can create disposable/temporary email addresses for various testing jobs.
Are you aware of postfix recipient_delimiter? It allows for disposable / wild card addresses. If enabled in postfix, you setup a mailbox user like barbaz@mydomain.com and any address with that user and the delimiter would still get delivered to that user.
barbaz@mydomain.com -> barbaz@mydomain.com barbaz+randomtext@mydomain.com -> barbaz@mydomain.com barbaz+test1@mydomain.com -> barbaz@mydomain.comYou can change the + to any symbol you want postfix to look out for.
We were using this approach on a different domain but our issue was that we have multiple people on the same piece of work and so they needed to share access to all of the mails. We decided on the approach I'm describing as we also wanted to have control at the DNS level to do this such as expiring addresses.
I think my "creating users" was me wanting to make sure that when postfix passes an email for "barbaz@mydomain.com" to Dovecot, then Dovecot will store it and wait for someone to come along and impersonate barbaz. i.e. "barbaz" doesn't have to exist as a user already before Dovecot will store the mail.
If you are using LMTP dovecot will only accept emails from postfix that it can lookup the /directory/path to from one of the userdb{} or passdb{} sections. If dovecot can not find a match in any of the userdb{} or passdb{} it will reject the email as user unknown causing postfix to send a undeliverable notice email back to the envelope sender address, also known as back-scatter. I am not aware of a way to use wildcard addresses in dovecot userdb{}, i don't think its possible but i don't know what i don't know.
So I think this will be the main issue now - there's no way of knowing the addresses ahead of time, so it sounds like I'll need to add them to userdb{} when they hit postfix and before they get passed to dovecot.
For my sins I'm building this on Kubernetes so dovecot is on a separate "machine" at the moment. The userdb will be in postgres, as I'm using that for other things, so I guess I'll need to update that in postfix somewhere. This is a fairly low volume system, so I can probably take the hit of a DB query per email.
Currently postfix doesn't even seem to be attempting to talk to dovecot but that's one for the postfix list.
Thanks again for the help.
Cheers,
Felix