Design Check

justina colmena ~biz justina at
Thu Oct 28 06:10:18 EEST 2021

Interesting. Have you looked at this?

[People have too much "flair" and rep points and I can't participate in those stackexchange discussions or ask or answer like I used to.]

On October 27, 2021 3:15:01 PM AKDT, dovecot at wrote:
>> I think your approach would work, however, if I set
>> up aliases similar to:
>> -> barbaz at
>> 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 at
>> one stumbling block could be that we don't
>> know the various subdomains ahead of time.
>> The subdomain can be any value that the user
>> wants, and we don't want them to have to
>> precreate them before they can use an address
>Best to my knowledge this is not possible with postfix. But ask the 
>postfix mailing list to get a definitive answer. In postfix you have to 
>tell it the domains it accepts mail for, anything else it considers 
>relaying. Otherwise how does postfix know that email is meant to be 
>saved here or it is just passing through and you want postfix to query 
>DNS to find out where it goes (if relaying is even allowed).
>> 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 at and any address with that user and the 
>delimiter would still get delivered to that user.
>    barbaz at -> barbaz at
>    barbaz+randomtext at -> barbaz at
>    barbaz+test1 at -> barbaz at
>You can change the + to any symbol you want postfix to look out for.
>> I think my "creating users" was me wanting to make sure that when 
>> postfix
>> passes an email for "barbaz at" 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.

Sent from my Android device with K-9 Mail. Please excuse my brevity.
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