lmtp and recipient_delimiter

[Martin Johannes Dauser]

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