lmtp and recipient_delimiter

[Martin Johannes Dauser]

On Sonntag, 15. März 2020 22:37:40 CET Martin Johannes Dauser wrote:
> On Sonntag, 15. März 2020 21:43:08 CET Juri Haberland wrote:
> > On 15/03/2020 21:26, GMX Account wrote:
> > > have a look at this:
> > > 
> > > http://www.postfix.org/postconf.5.html#recipient_delimiter
> > > 
> > > [...]When the recipient_delimiter [1] set contains multiple characters
> > > (Postfix 2.11 and later), a user name or .forward file name is
> > > separated from its extension by the first character that matches the
> > > recipient_delimiter [1] set.[...]
> > 
> > Uhm, yes, I know what this option should do, but what happens, if I
> > already have a user with e.g. a hyphen (-) in its name (e.g. foo-bar)
> > and I set recipient_delimiter to "-"?
> > 
> > Will this character become a somewhat illegal character for usernames in
> > the user database?
> > 
> > 
> > Cheers,
> > 
> >   Juri
> 
> Yes, of course . By setting the delimiter "-", the address foo-bar at ex.tld
> becomes foo at ex.tld . Postfix seems to have a special interpretation of "+-"
> as it is compatible to qmail extension (another smtp server), which seems
> to have "-" hardcoded as delimiter. So I guess postfix is using "+" OR "-"
> as delimiter...
> 
> foo-bar at ex.tld
> foo+bar at ex.tld
> foo+-bar at ex.tld
> ... would all be sent to foo at ex.tld  ??
> 
> From  http://www.postfix.org/postconf.5.html#recipient_delimiter
> # Handle both Postfix and qmail extensions (Postfix 2.11 and later).
> recipient_delimiter = +-
> 
> (Who would need such a compatibility option -- I mean where is the use case
> ?!) Martin

Ah, answering my own post, sk71 already gave the hint:

When the recipient_delimiter set contains multiple characters , a FILE NAME is separated from its extension by the FIRST CHARACTER THAT MATCHES the recipient_delimiter set. So postfix will act similar to qmail and check files: "the delivery instructions for username-extension are in ~username/.qmail-extension."

So setting the delimiter to "+-" postfix will interpret 
  * foo-bar at ex.tld as an email for foo at ex.tld and will check a file matching "bar".
  * foo+bar at ex.tld  -> foo at ex.tld, file matching "bar"
  * foo+-bar at ex.tls -> foo at ex.tld, file matching "-bar"
  * foo-+bar at ex.tls -> foo at ex.tld, file matching "+bar"

Well and you might want to use that when transfering from/to qmail.

Martin