Overview

Since at least January of 2024, numerous reports have identified that Spamcop – an online spam blacklist – appears to be blocking large numbers of IP Addresses used by Microsoft 365’s services across the 40.107.0.0/16 IP range.

It’s understood that Spamcop has blocked these IPs due to the high rates of spam originating from Microsoft’s servers.

Emails blocked by Spamcop will generally receive a bounceback notification with an error message such as the following example;

Remote server returned '550 5.7.514 Decision Engine classified the mail item was rejected because of IP Block (from outbound normal IP pools) -> 554 5.7.1 Service unavailable; Client host [40.107.107.107] blocked using bl.spamcop.net; Blocked - see https://www.spamcop.net/bl.shtml?40.107.107.107'

The following Spamcop link shows the details regarding the above example – including the cause of the listing, how many days the IP has been blacklisted for recently, and related IPs;
https://www.spamcop.net/w3m?action=blcheck&ip=40.107.107.107

Option 1 – Sender Requests New IP from Microsoft

During the course of assisting customers that use Microsoft 365 email hosting through ourselves, we’ve been in contact with Microsoft’s support team on this matter.

At this stage, the latest advice that Microsoft has given us is that the sender must submit a support request to Microsoft’s team, requesting that their 365 Tenancy’s IP Address be rotated to a different IP that is not currently blacklisted by Spamcop.

If you are a Conetix customer who has your Microsoft 365 email hosting services through ourselves, you may contact ourselves on to ask that we submit the request on your behalf.

Otherwise if the affected sender is not a Conetix customer (ie, one of your contacts that uses MS365 is having issues sending emails to you), they must contact Microsoft Support themselves.

Administrators can log into the 365 Admin Centre here:
https://portal.office.com/Adminportal/Home?#/support/requests
Then click ‘Help & Support‘ in the left-hand menu to open the support panel.

If you have a VPS hosted with Conetix you may alternatively opt to disable spam checks through Spamcop, however this comes with the following considerations that must be fully understood;

  • If you disable Spamcop checks on your VPS, this lowers the overall chance that spam, phishing, and other malicious emails will be successfully blocked before they reach your inbox.
  • As disabling the checks is a server-wide action, this means that if you have customers/clients hosted on your VPS, they will also be affected and therefore also more likely to receive malicious emails.
  • You are responsible for this action, and for anything that may result due to the disabling of Spamcop checks.

With the above in mind, you may submit a request to to ask that Spamcop checks to be disabled on your VPS.

Please note that if you do not have a VPS with Conetix (ie, you have a shared hosting plan), you must instead refer to Option 1.

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