> On 9 Sep 2019, at 16.17, Philipp Faeustlin via dovecot <dovecot@dovecot.org>
> wrote:
>
>> It is not recommended to rely on local-part case, but it is indeed
>> case-sensitive.
>> And this is to avoid such issues that postfix supports address
>> cleanup/canonicalisation before forwarding mails to dovecot.
>> ----------
>> RFC 5321:
>> "Local-part = Dot-string / Quoted-string ; MAY be case-sensitive
>> […]
>> While the above definition for Local-part is relatively permissive,
>> for maximum interoperability, a host that expects to receive mail
>> SHOULD avoid defining mailboxes where the Local-part requires (or
>> uses) the Quoted-string form or where the Local-part is case-sensitive."
>> And therefore “receive liberally” policy that wants to assume
>> case-insensitivity should single-case the address IN THE COMPARISON.
> The local-part MAY be case-sensitive, but in general I don't know any mail
> addresses where the case matters.
> Thus it is hard for me to understand, why this comparison of the vacation
> address is case-sensitive. Whether the final recipients address is also
> treated case-insensitive.
>
> If this has to be case-sensitive to be RFC compliant, then please create an
> option for admins or users to change the behavior to an case-insensitive
> comparison.
>
Just change auth_username_format = %Lu to make all addresses lowercase. That
should solve your problem.
Or if you REALLY REALLY want to have case-sensitive userpart, then use
auth_username_format = %n@%Ld
Sami