Fix lmtp_save_to_detail_mailbox to be case insensitive?

[Daniel Lange]

Am 21.05.22 um 23:30 schrieb dovecot at ptld.com:
> Dovecot accepts the mail from postfix via LMTP. Dovecot already found the valid recipient and accepted the email.

You need to make postfix pass the extension as lowercase to Dovecot.

See https://wiki.dovecot.org/LDA/Postfix :

An example using address extensions (ie user+extension at domain.com (don't 
forget to define the proper recipient_delimiter in Postfix's main.cf)) 
to deliver to the folder 'extension' in your maildir (If you wish to 
preserve the case of ${extension}, remove the 'hu' flags, ...

dovecot unix    -       n       n       -       -      pipe
   flags=DRhu user=vmail:vmail 
argv=/usr/local/libexec/dovecot/dovecot-lda -f ${sender} -d 
${user}@${nexthop} -m ${extension}