Network Upgrade: Access Control List (ACL) / Your action required

Posted by MailGuard on Jun 19, 2019 3:43:05 PM

In the near future, MailGuard will be performing an important network upgrade that requires action from its partners on behalf of end customers and clients.

Although MailGuard is a “set and forget” solution, an upgrade of this sort ensures your clients’ email feed is clean and uninterrupted.

This service is part of MailGuard’s ongoing commitment to enhance our users’ experience and to ensure all customers are served as effectively as possible.

Here’s a summary of what you need to know about the upgrade: 

What's happening?

MailGuard's client-facing email relays are being upgraded with some hosts being decommissioned.

The list of hosts (IP addresses) from which clients can expect to get their clean email delivered – known as the Access Control List (ACL) – is changing. The number of IP addresses will be reduced from 12 to 6.

We strongly recommend that your clients update to the new ACL as soon as possible.

How you can implement this right now:

The ACL is most commonly applied at the Office 365/ Exchange/ Mail Server or the perimeter firewall level.

To make this change,

  • Ensure that the list of “New ACL” IP addresses below are the only ones that remain in your records.
  • Ensure that any other IP addresses previously provided by MailGuard, that are not listed below, are removed. They can be removed, AND, are not actively processing emails at all at this time.
    • If there are any other IP addresses in the client’s ACL – please review them as a priority – and decide if they need to remain (trusted sources of emails, website, internal systems, etc), or if they too can be removed.




When does this need to be completed?

All updates to ACL’s listed in this post need to be completed by September 27th, 2019. Failure to complete these changes, places the client’s server at risk of accepting email from non-trusted email sources. 

Why are we telling you now?

We want to provide our partners ample notice so that you can make the changes at a time that’s convenient to your business and/or team.

Mass communications containing in-depth details about the nature and requirements of this upgrade will be sent out to partners and customers soon.

In the meantime, if you have any questions, please contact MailGuard support at


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