Outlook incorrectly autofilling a user name in emails and meeting invitations

bimmerdriver 6 Reputation points
2020-12-20T19:57:17.067+00:00

I work for a large multinational company which uses Office 365 Professional Plus. We use Outlook / Exchange for email. My computer currently has Windows 10 version 1909 and Outlook for Office 365 MSO (16.12527.21294) 32 bit installed. IT support is outsourced to another large multinational company. The IT helpdesk is an offshore call center. I’m experiencing a problem and the IT helpdesk doesn’t seem to have a solution, so I thought I would try here.

Normally, when I send an email or invite someone to a meeting, I type their first name and Outlook autofills Lastname, Firstname. In particular, when I do this while creating a meeting invitation, I can see the free / busy information for the user. Occasionally, Outlook does not autofill a user correctly. In this case, it autofills Firstname Lastname (firstname.lastname@companyname.com). In this case, the free / busy information is not available. Normally, autofill works correctly. However, I’m having a problem where Outlook is incorrectly autofilling a particular user on a consistent basis. I can force it to autofill properly by typing lastname first. If I type firstname first, it will always autofill incorrectly. It’s possible to create an email or meeting invitation for “both” of these users, but Outlook will automatically remove whichever one I entered second after a few minutes. If I entered the incorrect username first, that one will remain in the email address or meeting invitation.

As I said, there have been a few random occasions where this happens for other users, but it has always been temporary. However, for this particular user, it happens on a consistent basis.

IT has suggested several “fixes”, none of which permanently fix the problem.

The first fix was to empty the auto-complete list. This works, but only temporarily.

When the first fix proved to be temporary, the second fix was to delete the Outlook RoamCache. This also works, but only temporarily.

When the first and second fixes didn’t work, the third fix was to delete and recreate the OST for my profile. This took several days because I work remotely. This did not fix the problem.

Another fix was to delete the address book. This did not fix the problem.

Another fix was to delete and recreate the contact for the user. This did not fix the problem.

Another fix was to repair Office 365. This did not fix the problem so they tried reinstalling Office 365. That also did not fix the problem.

They also checked the profile of the user. They found some sort of inconsistency in the profile, which they corrected, but it did not fix the problem.

This does not happen in Outlook web, only in Outlook desktop.

Does anyone have an idea of what could be causing this?

Outlook Management
Outlook Management
Outlook: A family of Microsoft email and calendar products.Management: The act or process of organizing, handling, directing or controlling something.
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  1. JeffYang-MSFT 6,241 Reputation points
    2020-12-21T06:46:34.407+00:00

    Hi @bimmerdriver ,

    Welcome to Microsoft Q&A forum.

    Before going further, the AutoComplete list for Outlook is specific to Outlook and is not shared by Outlook Web App (OWA). OWA maintains its own AutoComplete list. So, the AutoComplete feature in OWA might not be useful for us to troubleshoot our client issue.

    As you have mentioned, the "empty the auto-complete list" method and the "delete the Outlook Roam Cache" are both common method for AutoComplete issues in Outlook client. Since it could indeed work for a while, so we might be able to refer that the issue should be related to the AutoComplete cache in your computer.

    It’s possible to create an email or meeting invitation for “both” of these users, but Outlook will automatically remove whichever one I entered second after a few minutes.

    Are both the "normal" and "abnormal" AutoComplete entries all real-existed user's email address? Or the "abnormal" one is an empty email address?
    According to my tests in my Outlook 365, when sending emails to both valid email address and invalid email address, Outlook will not automatically remove any entries in the "To" list, we will just receive a NDR messages about the invalid email address but all the addresses are still remained in the "To" list. As I know, there could be some add-ins in your Outlook client that influence your AutoComplete cache and cause issues like this, so it is suggested to empty your AutoComplete list and start your Outlook in safe mode (Press Win + R, type “outlook /safe”, press Enter.) and see if the issue continues.

    By the way, are you using Outlook desktop client along with other third-party programs? Antivirus software and other third-party programs might also cause issues like that. So, if possible, please try to empty your AutoComplete list and exit your Antivirus software to see if this issue could still be reproduced.


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  2. bimmerdriver 6 Reputation points
    2020-12-22T21:17:59.113+00:00

    Sorry for the delay to reply. After sending the original post, I cleared the auto-complete cache and the problem hasn't returned (yet). It has always returned before, so I expect that it will.

    The only visible distinction between the normal and abnormal email addresses is the format. Normal is Lastname, Firstname. Abnormal is Firstname Lastname (firstname.lastname@companyname.com). The correct email address for the normal case is exactly the same. There are a couple of things I noticed about the abnormal format. In a meeting invitation, the free/busy information for the abnormal email address is not available. Also, the contact information for the normal email address is populated with details. For the abnormal email address, the contact information is empty, except for the name and email address.

    When the problem returns (as it always has previously), I will try send an email to the abnormal email address to see if the recipient receives it.

    Also, I was looking at my previous calendar. I noticed that someone who attends meetings that I and the problematic email address also attend and I observed that the abnormal email address was used. Is it possible that Outlook is caching this email address because it appeared in a meeting invitation? This seems to be a bug in Outlook.

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  3. JeffYang-MSFT 6,241 Reputation points
    2020-12-23T08:57:31.617+00:00

    Hi @bimmerdriver ,

    Thanks for your reply.

    In order to avoid misunderstanding, I am trying to retell your issue here, please kindly check if I have understood your issue correctly:
    you have an email recipient whose "Display Name" is lastname.firstname, "Email Address" is firstname.lastname@companyname.com.
    Normally, when typing the firstname in "To" list, you could successfully find the entry. When this issue occurs, you would get an entry whose "Display Name" is firstname.lastname, "Email Address" is the same firstname.lastname@companyname.com, right? If I still got any misunderstanding, please kindly try to provide me with screenshots of your issue for further research.

    I noticed that someone who attends meetings that I and the problematic email address also attend and I observed that the abnormal email address was used. Is it possible that Outlook is caching this email address because it appeared in a meeting invitation?

    I did some search but have not found any official documents explained your issue. Can you reproduce this issue if you make other users send an Outlook meeting to both you and the abnormal email address? I tried tests in my Outlook, seems could not reproduce your issue either.

    By the way, just as what I mentioned before, since you can work fine for now, it is suggested for you to disable all your Outlook add-ins and temporarily exit other Outlook-related third-party programs to see if this issue would come back again. (Note: Since the web site is not hosted by Microsoft, the link may change without notice. Microsoft does not guarantee the accuracy of this information.)

    Any update, please feel free to post back.


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  4. bimmerdriver 6 Reputation points
    2020-12-24T01:07:23.893+00:00

    I will explain again. In the email system, all email addresses are firstname.lastname@companyname.com and a resolved name is displayed by Outlook as "Lastname, Firstname" (excluding the ""). Normally, I enter an email address (for an email or meeting invitation) by typing firstname first and it resolves as above. There are some cases where an email address does not resolve properly. In this case, it is displayed by Outlook as "Firstname Lastname (firstname.lastname@companyname.com)" (excluding the ""). When this happens in a meeting invitation, the free/busy information for the user is not available. This has happened occasionally / temporarily for some random users, but it happens consistently for one particular user.

    In this case, if I am sending an email or creating a meeting invitation, if I enter firstname, it resolves incorrectly. I can force Outlook to resolve it correctly by entering lastname, firstname. If I enter both in either order, after a few minutes, Outlook will remove the second. In a meeting invitation, the entry that is correctly resolved will display the free/busy information, but the other will say free/busy information is unavailable.

    If I select the email address from the address book, it will always be correctly resolved.

    The other difference is that the contact information for the entry that is correctly resolved will have the full details, such as address and telephone number, which are in the address book. The contact information for the entry that is not correctly resolved only has the name and email address, not the other information.

    I can temporarily make this go away by clearing the auto-complete cache in Outlook. This is temporary. The problem always returns after a day or two. (It has already returned, since the last post.) I will check the inbox and calendar to see if there are any emails or meetings from the past couple of days which have the incorrectly resolved email address.

    I'm completely at a loss about what is causing this strange behavior.

    I will check for add-ons and report back what add-ons are installed.

    Thank you for your support.