[Sophos Notification] Advisory: Central Email - Outbound Email Rate-Limit (Mail flood detected) notifications and bounce-backs

Hi Community,


Sophos has received reports from some customers experiencing problems sending out emails to a large number of bulk recipients.


A similar bounce back may be seen from the sender before February 12th at 15.00 UTC.

  • 554 5.7.28 Mail flood detected;

The following notification may also be seen on the administrator dashboard:

Current status

As of 15:00 UTC February 12th, 2020, the thresholds have been reverted.

What to do

In preparation of the rate-limits being introduced, bulk email senders can request bulk sender privileges to high volume mailboxes.

Under Central Email > Mailboxes > Select the mailbox and click Request bulk sender privileges and fill out the request form.

Next update

This article will be updated when information becomes available.


  • Thanks for the notification before turning this on - NOT!

    What's the turnaround time on the request - been > 4 hours and still status pending.

    What constitutes a bulk load?  We snagged on < 25 invoices sent out this morning - 8 rejected with Mail flood detected error.