You can use

protocol lmtp { mail_utf8_extensions=yes }

or protocol lda

to enable it for lmtp (or lda) only.

Aki

On 16/02/2026 21:05 EET max.wriedt--- via dovecot <dovecot@dovecot.org> wrote:

i just upgraded my 2.3 installation to 2.4. I like to be bleeding edge and i want to use SMTPUTF8.

I came across problems with mailboxes that have german umlauts. when enabling "mail_utf8_extensions=yes" e.g. Microsoft Outlook gives me mUTF-7 encoded folder names. Also the folder names when list via openssl s_client are encoded in mUTF-7. Am i missing something or can i disable utf8 for IMAP (UTF8=ACCEPT) only, but keep for LMTP Transport/SMTPUTF8 from postfix to dovecot?

I am using mdbox format as storage, if that matters.

My namespace config (shortened): namespace inbox { inbox = yes type = private

#mailbox_list_utf8 = yes # also tried this -> when folder didn't exist before it would create a new one with utf8, no matter mail_utf8_extensions is on or off

mailbox Drafts { auto = no special_use = \Drafts } mailbox Entw&APw-rfe { special_use = \Drafts } mailbox Entw%26APw-rfe { special_use = \Drafts } mailbox Entw\&APw-rfe { special_use = \Drafts } mailbox Entwürfe { auto = create special_use = \Drafts } mailbox Trash { auto = no special_use = \Trash quota_storage_percentage = 110 } mailbox "Gel&APY-schte Elemente" { special_use = \Trash quota_storage_percentage = 110 } mailbox "Gelöschte Elemente" { auto = subscribe special_use = \Trash quota_storage_percentage = 110 } mailbox Sent { auto = no special_use = \Sent } mailbox Archiv { auto = subscribe special_use = \Archive }

mailbox Spam { special_use = \Junk auto = no } }

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On 16. Feb 2026, at 21.05, max.wriedt--- via dovecot <dovecot@dovecot.org> wrote:

i just upgraded my 2.3 installation to 2.4. I like to be bleeding edge and i want to use SMTPUTF8.

I came across problems with mailboxes that have german umlauts. when enabling "mail_utf8_extensions=yes" e.g. Microsoft Outlook gives me mUTF-7 encoded folder names. Also the folder names when list via openssl s_client are encoded in mUTF-7. Am i missing something or can i disable utf8 for IMAP (UTF8=ACCEPT) only, but keep for LMTP Transport/SMTPUTF8 from postfix to dovecot?

IMAP UTF8 support is still missing various things. UTF8 mailbox names are already implemented in git main, but they are not in any release yet. There are other parts still not implemented though.