O prompt é codificado na origem ( nnimap.el
):
(defun nnimap-credentials (address ports user)
(let* ((auth-source-creation-prompts
'((user . "IMAP user at %h: ")
(secret . "IMAP password for %u@%h: ")))
(found (nth 0 (auth-source-search :max 1
:host address
:port ports
:user user
:require '(:user :secret)
:create t))))
(if found
(list (plist-get found :user)
(let ((secret (plist-get found :secret)))
(if (functionp secret)
(funcall secret)
secret))
(plist-get found :save-function))
nil)))
Portanto, parece que a única maneira de mudar isso é redefinir a função e modificar o prompt para ser apenas "IMAP password for %u: "
.