kumomta/docs/reference/headermap/set_sender.md

set_sender

headers:set_sender(VALUE)

{{since('2025.10.06-5ec871ab')}}

Assign VALUE to the Sender header.

VALUE may be either a string or a Mailbox.

If you assign using a string, the string will be parsed and validated as being compatible with Mailbox before allowing the assigment to proceed.