EMClient NTLM Error

Problem reported by SEIT - 7/28/2026 at 12:20 AM

Being Fixed

Hello everyone,

There has been a recent surge in complaints from eMclient users having authentication issues. The most prevalent and consistent error given is "ERR NTLM failure".

Has anyone figured out any fix to this ?

4 Replies

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J. LaDow Replied

7/28/2026 at 6:34 AM

We really need a way to disable NTLM in general (or at least NTLM v1) on the server level.

This is still causing us tons of problems with iOS clients...

MailEnable survivor / convert --

Andrew Barker Replied

7/28/2026 at 7:03 AM

Employee Post

Which protocols are you seeing issues with? We recently identified a bug in NTLM authentication for POP connections, but it wouldn't affect other protocols. A fix should be included in the next release.

Since this is an issue we are aware of, I've changed this thread to a Problem and marked it as Being Fixed.

Andrew Barker
Lead Software Developer
SmarterTools Inc.
www.smartertools.com

SEIT Replied

7/28/2026 at 7:40 AM

@Andrew Barker

So far the complaints have come from users with POP connections.

Millennium Systems Replied

7/28/2026 at 8:47 AM

For the time being you can fix this on the eM Client side.

Go to Menu > Accounts > choose the specific account from the list
Click on the tab Diagnostics
In the Advanced Options sections put the following in the Parameters field:

--force-pop-auth PLAIN

Click on Save, close and restart eM Client

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