Say goodbye to the Remote Mailslot protocol in Windows 11

by Alexandru Poloboc

Alexandru Poloboc

With an overpowering desire to always get to the bottom of things and uncover the truth, Alex spent most of his time working as a news reporter, anchor,… read more

  • Microsoft recently released a brand new Insider build for the Canary Channel.
  • Through this build, the company is deprecating the Remote Maislot protocol.
  • The process has already started and it will continue until the feature is removed.


We’ve recently been talking about a lot of the features that Microsoft plans to add to its latest operating system, Windows 11.

However, don’t think that Microsoft will only add and take nothing back. In fact, the software giant is starting to remove quite a few of the older features.

After announcing that it plans to retire the MSDT function before the release of Windows 12, Redmond developers deliver some more bad news.

We’re actually talking about the Remote Mailslot legacy tool. and trust us when we say that you will actually want to know about this.

Microsoft has started deprecating this feature in build 25314

As we’re sure you remember, just a couple of days ago, Microsoft released build 25314 to its new Canary Channel.

This above-mentioned build contains a lot of new features including access key shortcuts and recommendations in File Explorer, along with LSA protection enablement.

Not to mention that there are also indications of upcoming improvements to Taskbar and Windows Settings as well.

However, notably on the security side, the Redmond-based tech company is getting rid of the Remote Mailslot protocol.

Through a dedicated blog post, Microsoft’s Principal Program Manager Ned Pyle has noted that the legacy Remote Mailslot protocol has already been disabled by default in the latest Canary Channel release.

What should the solution be? Well, it appears that it will be deprecated shortly and will eventually be removed permanently.

The beginning of the end of Remote Mailslots - Microsoft Community Hub

In case you are unaware, Remote Mailslot is actually a protocol belonging to the days of LAN Manager DOS, that is, older than Windows NT.

Note that it follows a communication process where the mailslot server creates a mailslot that clients can write data to, but no longer than 424 bytes.

Keep in mind that a mailslot is ephemeral, once all the handles to it are closed, the mailslot and all the data in it get deleted.

Previously, mailslots were used to broadcast messages within a domain, with Pyle having particularly strong opinions about the legacy protocol, calling it disgusting and crap.

Thus, starting with build 25314 in the Canary Channel, Remote Mailslot is disabled by default and you’ll be greeted with an error if you attempt to access it.

Furthermore, if you come across errors, Pyle has recommended shouting at your software vendor and telling them to upgrade their software to join the 21st century.

And, while your vendor asks for time to concede to your demand, you can use run the following PowerShell command to get Remote Mailslot running again, with the knowledge that it is a major security risk to your organization:

PS C:\> Set-SmbClientConfiguration -EnableMailslots $true

Please remember that the removal of Remote Mailslot will not affect 99.97% of Windows customers since it is also used in tandem with the SMB1 protocol that has been disabled for the past several years too.

Microsoft has mentioned that more deprecations for similar and even bigger legacy protocols are on the way too.

What is your opinion on the current situation? Be sure to share your thoughts and ideas with us in the comments section located below.

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