On 06/04/2024 17:34 EEST lua8ds--- via dovecot <dovecot@dovecot.org> wrote: When a sender writes my email address with my username uppercase, e.g. USERNAME@name.com, in the to: field of their MUA, my mail server rejects that email. /var/log/mail.log prints: <USERNAME@redacted.com>: host mail.redacted.com[private/dovecot-lmtp] said: 550 5.1.1 > <USERNAME@redacted.com> User doesn't exist: USERNAME@redacted.com (in reply to RCPT TO > command) In the manual, I found that: auth_username_format Default: %Lu Formatting applied to username before querying the auth database. You can use the standard variables here. Examples: %Lu Lowercases the username [...] My current setting was not the default; I had: auth_username_format = %n So I updated that setting to: auth_username_format = %Lu expecting that %Lu would lowercase the username - and that my problem would be fixed. It does not though. Updating this setting not only prompts my email server to still reject USERNAME@redacted.com, but now also rejects (lowercase username) username@redacted.com (which my server had no issue receiving beforehand). So I reverted auth_username_format to: auth_username_format = %n Emails sent to username@redacted.com land in my mailbox again - but emails sent to USERNAME@redacted.com still don't. What can I try to troubleshoot? Which config file shall I share with you? _______________________________________________ dovecot mailing list -- dovecot@dovecot.org To unsubscribe send an email to dovecot-leave@dovecot.org Did you try %Ln? Aki