Why in Outlook 2016 IMAP (case-insensitve), renaming a folder from 'My folder' to 'My Folder' do not update non-exchange IMAP servers (case-sensitive) about the name change? Folder remain named 'My folder' server side which cause sync issues RRS feed

  • Question

  • In Outlook 2016 (case-insensitive), if an IMAP mailbox is setup connected to a non-Exchange case-sensitive server (from third party suppliers), why when a folder is renamed from 'My folder' to 'My Folder' (change case letter from f to F), Outlook does not inform the server of the name change causing discrepancies.

    I understand that Outlook is case-insensitive but it should not assume the IMAP server is and shall always update the server of name changes in all conditions.

    For Outlook I understand that 'My folder' and 'My Folder' are considered as the same folder, but for a server it is not necessarily the case if it is case sensitive (most IMAP servers are except perhaps MS Exchange) 'My folder' and 'My Folder' are two different folders server side.

    Unfortunately because of this discrepancy between Outlook (email client) and server, sync issues appears causing email not to be received/delayed in the worth scenarios... due to Outlook sync issues with some folders or their contents.

    In a similar way if a folder is named with a trailing space 'My Folder ' (which often happened after selecting some text by double clicking on it, Windows somehow tend to always add an extra space to the selection which when copy/paste to create folder name in Outlook end-up as part of the folder name but remain invisible to individual as the space character is invisible to the eye on screen if a following work is not set).

    Some how Outlook think a folder 'My Folder' (without trailing space) and 'My Folder ' (with trailing space) are the same 'My Folder' folder, while server side they are two distinct separate folders... once again causing a discrepancy between Outlook and the IMAP server... that causes numerous sync errors... (many sync error log messages created per day in the sync error folder in Outlook, without clear code or message indicating which folder/msg are at fault)...

    Multiple sync errors especially can eventually lead to new email received delivery in Outlook to be drastically delayed or simply blocked (instantly received on server, but appearing only one hour after or never in Outlook Inbox despite multiple send/receive actions from email client automatically or end-user manually).

    • Moved by Perry-Pan Friday, March 8, 2019 11:44 AM
    Thursday, March 7, 2019 2:09 PM

All replies

  • Hi SRL-Richard,

    I tested in my environment (IMAP account, Outlook 2016) but cannot reproduce what is described in your thread. So I’m thinking that there may be a problem during the synchronization process.
    After changing folder names or creating new folders, we can manually update folder list and then check if folders display correctly on the web mail.
    To do this, please click Folder tab > Update Folder List.

    Besides, if possible, it is suggested to configure the your email account on another computer and see if there is any difference. Or you can configure a new IMAP email account on your Outlook and test again.

    Any update, please feel free to post back.


    Aidan Wang

    Please remember to mark the replies as answers if they helped. If you have feedback for TechNet Subscriber Support, contact tnsf@microsoft.com.

    Click here to learn more. Visit the dedicated forum to share, explore and talk to experts about Microsoft Teams.

    Friday, March 8, 2019 9:45 AM
  • Hi Aidan,

    Which IMAP server did you use to do your test? If it is Microsoft Exchange it is irrelevant to the point made here... as I precised in the title that most problems come by using Outlook with third-party IMAP servers...

    The problem is not the display of the folder it is the synchronisation process via IMAP protocol... of the folder with its counter part on the server... Sync Error issues...

    As indicated it happens with trailing space in folder names, or when using strange character such as & in some circumstances... we are still seeing such issue in Outlook 2019... running on Windows 10 Pro x64... with Cyrus IMAP server as back-end... running on Linux OS...

    There are a lot of post on Internet with people experiencing synchronisation issue with their IMAP account in Outlook... the issues described here is more likely the reason of such situations...

    I think the problem is that when you create a folder in Windows with a trailing space... let say 'MyFolder ', Windows will save it as 'MyFolder' and so does Outlook more like and certainly in its cache... but Outlook during synchronisation with the server order it to create the folder 'MyFolder ' with the trailing space, which the server does as instructed... and that then create a discrepancy between Outlook and the server...

    That mean Outlook when creating folder on Windows (in its cache) and sending IMAP command to  the server to create the folder does not currently trim the folder name to remove any pre/post spaces in folder name (the same way Windows does) prior sending create folder commands especially via IMAP, so folder name on Windows Outlook cache and backend server would always NOT be the same currently while if the folder name was trimmed such issue would not happen... this is more likely a bug in Outlook.

    The same as Windows/Outlook is case insensitive and does not make a difference between MyFolder, myFolder or myFolder, it would still instruct such difference to the server via the IMAP protocol to the server which may be case sensitive (Linux is case sensitive by default) causing again a discrepancy... Outlook shall be able to handle such situation via the IMAP protocol more thoroughly... and update its cache accordingly... so if end-user rename myfolder into MyFolder... not just change the display in Outlook and its cache but also instruct the server to do so via IMAP protocol as well...

    IMAP Protocol was working fine and well in Outlook 2010... I am not sure why Microsoft had to re-invent the wheel starting from Outlook 2013 which IMAP protocol was faulty and not fit for purpose (e.g not sending proper IMAP command to delete a folder!!!) till 2019 version where implementation still cause synchronisation error depending on how end-user name folders!!!

    Is that something Microsoft can look into and fix?


    Friday, August 16, 2019 10:00 PM