The same here in Greece.

The only Outlook version which respects open standards concerning the IMAP protocol is Outlook 2010. We thought at first that Outlook 2013 would also be compatible with dovecot. Yet, as said, it seems to be a Microsoft company (internal) policy, not to comply with standards, since this would bring their "tower of cards" down. We hoped that Outlook 2016 would make a difference, or at least Outlook 2019, but none of the sort happened.

What is the exact problem? Well, here it is: Many times, users create folders with non-compatible characters in their folder names, either slashes or dots, etc. Outlook accepts these characters as valid, while dovecot will not. Yet Outlook creates the folder for the user and the user thinks he can use the folder, although the folder does not exist on the server. The user stores emails in the folder and uses it, until one day he either logs in via his webmail and does not see the specified folder. He then does not worry very much, since he can still work from his PC where Outlook is installed. Once the PC needs to have his hard disk replaced due to a failure, then he/she discovers that his emails are lost forever.

Anyway, we do have a company central email storage for all emails using copies of send and received emails, but even that would have him re-organise his emails into folders for a whole year or more, so this is another complain we have. Normally Outlook should not create the folder if the server does not accept the peculiar characters, but I believe that Microsoft has overlooked this.

Even if we are notified that a user has a problem of lost folders in his webmail, with what he may see in his Outlook client, we do not know what to do to fix the problem.

We have search to find options as to restrict folder allowed characters but could not find any option.

Another problem is that Outlook, including Outlook 2010, would automatically subscribe a newly created folder. This is a problem, because it means that the Outlook application will download emails for subscribed folders, usually exceeding limits, which should be re-set using the registry. If your users create many folders per day, then they have a lot of subscribed folders. Subscribed folders are looked up for new emails, and the application starts to slow down, and users again complain.

Thunderbird is far better with IMAP protocol.

Yet Microsoft has hypnotised most of the users into seen Outlook application as better.

Kind regards to all,

Panos. On 13/1/2022 18:38, Michael Peddemors wrote:

All I can add to this is anecdotal, from what we hear from ISP's and Telco's, and over the last year changes to the way Outlook behaves, everything from how it does auto discovery and setup, to smaller issues with SSL/TLS, make it seem that 'interoperability' is not a priority for some of the monsters in the industry.

This is NOT a dovecot issue, but a worrisome trend in the industry.

"If you want product XX to work flawlessly, you need to use product XX"

However, we are going to still have to play in their sandbox, as Outlook is still prevalent in the business community.

My 'tin foil hat' suggests that it is even a business tactic by some companies, to reduce competition.  Those that are NOT working for "monsters" need to support each other, by adopting more open standard tools, which means we should all try to use open products, both email providers, and email clients.

Sorry, that doesn't help your situation though. Other than encouraging the use of alternative email clients ;) But for the most part, expect users not to understand.  They just want things to work.

On 2022-01-13 2:07 a.m., Vladislav Kurz wrote:

...

Dear colleagues,

what is your experience regarding using outlook (2016/365) as IMAP client and dovecot on server side?

We have sync issues with outlook vs. cyrus IMAP server, and we consider moving to dovecot. But before that I'd like to hear from others if this combination works well. Especially if users have large and bushy mailboxes (>10 GB, >100 mailboxes), two mailboxes (accounts) on the same server.

I don't want to do the migration just to find out that it is general issue of outlook vs. any IMAP server.

On 17. Jan 2022, at 10.31, Vladislav Kurz vladislav.kurz@webstep.net wrote:

Dne 15. 01. 22 v 18:46 Panayiotis Fafakos napsal(a):

...

The same here in Greece. The only Outlook version which respects open standards concerning the IMAP protocol is Outlook 2010. We thought at first that Outlook 2013 would also be compatible with dovecot. Yet, as said, it seems to be a Microsoft company (internal) policy, not to comply with standards, since this would bring their "tower of cards" down. We hoped that Outlook 2016 would make a difference, or at least Outlook 2019, but none of the sort happened. What is the exact problem? Well, here it is: Many times, users create folders with non-compatible characters in their folder names, either slashes or dots, etc. Outlook accepts these characters as valid, while dovecot will not. Yet Outlook creates the folder for the user and the user thinks he can use the folder, although the folder does not exist on the server. The user stores emails in the folder and uses it, until one day he either logs in via his webmail and does not see the specified folder. He then does not worry very much, since he can still work from his PC where Outlook is installed. Once the PC needs to have his hard disk replaced due to a failure, then he/she discovers that his emails are lost forever.

Thanks for sharing your experience. We had exactly the same problem with Cyrus IMAP. Good to know this is not Cyrus' fault.

Please also note that atleast for M365 licensed version of Outlook for Mac (version 16.57) now forces sync to microsoft cloud by default when adding IMAP account:

https://imgur.com/a/sB3Kfu6 https://imgur.com/a/sB3Kfu6

(says in image: For better experience, your messages will be synced to the Microsoft cloud)

I cannot opt-out from this. (Just realised that this actually might be something forced by my employers Intune policies)

Sami

Please also note that atleast for M365 licensed version of Outlook for Mac (version 16.57) now forces sync to microsoft cloud by default when adding IMAP account:

https://imgur.com/a/sB3Kfu6

(says in image: For better experience, your messages will be synced to the Microsoft cloud)

I cannot opt-out from this. (Just realised that this actually might be something forced by my employers Intune policies)

And indeed after I continued to add the account the incoming IMAPS connection to my dovecot server came from 52.98.150.133 wwned by Microsoft.

I do no think it is related with settings. I have a 'airlocked' test environment with exch 2016 and I was surprised that the mobile outlook app is also connecting to the microsoft cloud. Which really surprised me, that must be against all GDPR legislation. Thus currently if you have an exchange server you can not get email on mobiles without using a 3rd party app. They are totally mental at microsoft.

On 1/17/22 9:58 AM, Sami Ketola wrote:

And indeed after I continued to add the account the incoming IMAPS connection to my dovecot server came from 52.98.150.133 wwned by Microsoft.

Sami

Noticed the same, 4 connection attempts from a Microsoft owned ip when setting up an e-Mail account with Outlook 2019 before it shows the option which account type you want to add.

Alex