Our odoo was configured to send email when a leave(time off) is approved. It was done using Automated actions.
From past 2,3 days it's not working. Below is the error getting from Odoo logs.

odoo.addons.mail.models.mail_mail: Mail with ID 9772 and Message-Id '' successfully sent
odoo.models.unlink: User #1 deleted mail.mail records with IDs: [9772]
odoo.addons.mail.models.mail_mail: Sent batch 1 emails via mail server ID #False

Any idea why odoo is deleting those records.