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

Overview

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

Applies to the following Sophos product(s) and version(s)
Sophos Central Email

Impact 

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.

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