IMAP is not working correctly on Outlook Office365. Error: "User is authenticated but not connected"

Hi Artur,

Just as information for you. I got some answer from the ticket. But I have to start from scratch, to get to somebody who understands the Office365 cloud system. I think I am at some kind of first level support. And they want to validate my client settings (via screenshots), however I have sent them the OpenSSL logs which clearly shows that it is not client dependent.

Hopefully there will be some answers later on.

Regards,

Robert

Hi Artur,

Did you got some information to your ticket? I am still struggling with the support.

The public support here was more willing to help than the Office 365 Ambassador which I am in contact with...

Regards,

Robert

Hi All,

In case anybody has trouble with the same problem. I share my results.

First of all the Microsoft payed support was not really willing to help although one of they payed services is not working correctly. I had to constantly prove that the problem is on server side. They were also not willing to give much information.

However after a couple of escalation rounds I find the following:

There is an IMAP Policy in place, which banns or restricts users if they behave "badly". What they check and what are the limits is for some insane reasons not public. However I managed to get the information that they check something similar -- but not fully the same -- as "Set-ThrottlingPolicy" function (which is on on-premise servers)

https://docs.microsoft.com/en-us/powershell/module/exchange/server-health-and-performance/set-throttlingpolicy

In my case IMAPMaxConcurrency limit was hit according to the support. Based on my measurements this limit is 15. My clients use only 1-1 connection which means I could not have reached the limit.

As further testing on my side, I have found that the server does not have dead connection detection. Which results that if I am using mobile internet and the phone switches between cells, it gets a new IP address, the old TCP connections are on server side open, but otherwise dead (half open connection). So the server thinks that I have reached the limit.

The Idle Timeout for the TCP connections is around 20 minutes. So I can do nothing till 20 minutes if I hit the limit.

Usually all industrial standard IMAP servers have "dead connection detection" which means that the server sends a NOOP (no operation) every ~2 minutes down to client, and if it does arrives it closes the dead connection.

Unfortunately Microsoft Exchange Server does not have such feature according to the support.

Workaround possibilities:

• You should reduce the number of connections to the server in you client. (This can be done in Thunderbird, and in most clients). This helps to reach the limit later, or not reach the limit at all.
• If you are using mobile internet as I do, you can try what I am doing. I have created an IMAP Proxy server on my own server, which is on a fixed internet line, and implemented a dead connection detection algorithm. So basically the functionality what is missing from Microsoft...(there are a couple of such proxies available on the internet, but I tried an own solution in our company)

I hope that helps.

Regards,

Robert

Hi

I experience a similar problem. Got a business Office365 account with a default password. Logged in through webinterface, chanced my password. Configured IMAP in Thunderbird/Linux and e-mail/Android, both worked like a charm.

Then, for some reason, my password had to be changed (SSO at the business). From then on webinterface works (with the new password of course), but the IMAP's don't work anymore, not with the new password, not with the old password. Removing en re-adding the account in Thunderbird didn't change anything.

I remember I had a similar problem with an account which forced to change the password every 3 months.

IMHO, MS doesn't maintain their IMAP access properly. There is some interface which doesn't update.

Regards

Guido

Dear Guido:

my look in the crystal ball says:

1. Your message will be split to another topic.
2. You will be asked to describe your problem.
3. There will be a private message, where it is said your admin should create a ticket somewhere else, because they cannot help you.

See here:

Other Split message

Best regards,

karl.ranseier