mailer-deamon spam with endless "Mail delivery failed"

[eoli3n]

For 3 month, I got a smtp authentication error that I didn't solve.

This is the DragonFly Mail Agent v0.11+ at domain.tld.

There was an error delivering your mail to <[email protected]>.

SMTP login to smtp.gmail.com failed

Message headers follow.

Received: from root (uid 0)
	(envelope-from [[email protected]](mailto:[email protected]))
	id 4235e
	by domain.tld (DragonFly Mail Agent v0.11+);
	Thu, 30 Jun 2022 03:55:57 +0200
To: root
Subject: nas daily security run output
Date: Thu, 30 Jun 2022 03:55:57 +0200
Message-Id: <[[email protected]](mailto:[email protected])>
From: <[[email protected]](mailto:[email protected])>

For each failed mail, dma now spam me with ~15 mail per day, everyday since 2 weeks.

This is what I got yesterday for exemple :

How to empty the queue ? I can't find anything with mail command

$ mail
No mail for root
$ ls /var/spool/mqueue
mail.core