Some users are discovering that Outlook sends winmail.dat files attached to messages when sending to contacts in their address book. Only Outlook on Windows desktop (all versions) is affected; messages sent from Outlook on the web or the Outlook app do not have the rogue winmail.dat file.
The problem: When sending email to any contacts from your address book in Outlook, some recipients receive a winmail.dat file attachment that shows up in some clients. Outlook should decode the winmail.dat file and correctly display any attachments, however, if not, the attachment icon may be displayed but no attachment is shown.
Gmail & Yahoo web mail should decode the winmail.dat file and show the attachment but HTML formatting will be lost. The Internet header will mention the winmail.dat file:
--_000_CY4PR12MB1750DB40ADDCB9EF8B1C7E1FCC5D0CY4PR12MB1750namp_
Content-Disposition: attachment; filename="winmail.dat"
Content-Transfer-Encoding: base64
Content-Type: application/ms-tnef; name="winmail.dat"
The keywords are "address book". If you select a contact and click the Email command on the ribbon or right-click and choose Create > Email from the context menu the message does not have the winmail.dat attachment.
As has always been the case, the winmail.dat file is more of a confusing nuisance than anything. The recipients receive an attachment and don't know what to do with it. (Correct answer: ignore it.) Note: Gmail and Yahoo recipients will lose HTML formatting but attachments will be accessible.
The usual fixes (listed at Outlook is Sending Winmail.dat Attachments) don't seem to work for most people or are only temporary and the problem returns. This is likely because the address book is the problem, not the contacts specifically.
More Information
Outlook is Sending Winmail.dat Attachments
Recipient receives a winmail.dat attachment when sending email from Outlook with Outlook.com account
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51 Comments on "Outlook.com Winmail.dat Bug"
One more bit of information. I also have several .PST files with only contacts in them. The "Display As" field in those files was not changed.
Yes, only outlook.com account should be affected by this bug.
>> If I call up the contact, blank the "Display As" field and hit TAB, the "Display As" field is changed to "John Smith - Contoso (JSmith@Contoso.com)". Note the "dash company" that is inserted.
Are you using more than one computer? If you edit the contact on a second computer, it shows up with the company name on the other computers. Editing it fixes it on that computer, but the company name version syncs to the others... it goes round and round. I hadn't noticed it blanking out though. Will see if i can repro.
At this time, i don't have any additional information on the status of a fix.
Microsoft's changeover to the Exchange platform for Outlook.com has been a total screw-up. They forced everybody to rebuild their .OST files, but it was impossible to do the rebuild with Two-Factor Authentication turned on. I had to disable 2FA, and I haven't been brave enough to turn it back on. I'm afraid it would break Outlook/Outlook.com again.
if you use 2-factor, you need to use the app password in outlook. At this time, Outlook won't pop up the second screen.
I can't remember the details, but the app password wouldn't work either. I ended up having to disable 2FA.
Just using one computer. (Lenovo ThinkPad T440s, Win10 Pro)
Syncing with a smart phone or editing contacts in outlook on the web?
Outlook 2016Outlook.comOutlook (Android)Android Contacts. All editing is done in Outlook 2016. (Contacts can't be edited in Outlook (Android), of course. Grumble, grumble.)
I also get a whole bunch of weird errors if I run Microsoft OffCAT against Outlook 2016. I can send you a screenshot if you like.
There are a lot of errors in the offcat - i would definitely disable the norton plugin. not sure if it is causing all of your problems, but it is not needed and can cause problems.
Some of these errors may be unique to outlook.com (due to features turned off for consumer accounts), but it also says you are delivering exchange mail to a pst - you should be using the mailbox cache.
If autoaccount setup doesn't work, you need to delete a value from the registry...
I did disable the Norton Anti-Spam plugin, both in Outlook 2016 and Norton.
i would try a separate profile with just one of the accounts in it - run offcat on it and see what comes up. Definitely sounds like offcat is screwy, but I don't know if it's due to the accounts in the profile or if its just screwy.
yeah, please on the screenshot. offcat should be erroring.
Where is the upload link? (Or am I staring at it?)
FYI - I am not getting notifications of replies, possibly because the Commenting System can't handle my unusual e-mail address.
i don't think the smtp server is blocking .name extensions, but i will double check on it.
You might be staring at it - or it's not visible due to caching or something out of your control.
It's just to the bottom right of this text field. If you don't see it, try using a different browser.
Got it. Unfortunately I can't upload a PDF or an .offx (OffCAT export) file. Can you PM another method/address?
I temporarily turned PDF support on - i don't normally allow anything but images for security reasons.
Sending the PDF. Unable to send the .offx. OK to pull up the drawbridge.
Still no notifications.
There are a lot of confirmations being sent - actually, it looks like maybe you are subscribing to a specific comment (but I could be misreading it). There were 9 confirmations and only one accepted - i accepted the others - so if you get 9 copies of replies, that is why. It's sent via exchange server - i ran a message trace and the confirmations were all delivered but no actual comments (that is why i think it is for a specific comment). Will check the trace on this...
Could be operator error. I subscribed on the initial post, but each reply also has a "Notify of new replies to the comment" checkbox. I'm a belt and suspenders kind of technoid, so I've been checking that box and confirming the subscription after each reply. I won't do it for this reply to see what happens.
I did receive your test message.
Anything useful in the barrage of OffCAT errors? Any update from Microsoft about them fixing this anal trauma (and undoing the damage to the "Display As" field)? Patch Tuesday is only a week away.
They have not said how soon, so my money is not this week. i will check it in the next insider build (usually out on Thurs/Fri) - they are usually about 4 weeks ahead of general availability.
I just noticed that Microsoft also screwed up the "File As" field in all my contacts. It was changed from "Smith, John (Contoso)" to "Smith, John(Contoso)"....with no space between John and the open parentheses. As a result, the name and company appear run together on one line in the Contacts instead of on two lines.
If you do have a communication channel with Microsoft, you might suggest that they do some research on such interesting topics as "Quality Assurance" and "Regression Testing."
I hadn't noticed that - will let them know. Thanks.
Any update on the progress of Microsoft's rectal encephalectomy? I'm getting really tired of having to remember to flip over to Outlook.com if I need to send an attachment.
i haven't heard - will check the latest insider build to see if it fixed it. (Sending from the contact should work correctly.)
Something else appears to be broken. I received a marketing e-mail from a local nursery with lots of pretty pictures and forwarded it to my wife from Outlook 2016. All she got was links. When I forwarded the same e-mail from Outlook.com it was fine. I confirmed this with a different forwarded e-mail with embedded pictures. The links to the pictures in the nursery marketing e-mail were to sendgrid.net. The links in the second test e-mail were to mailchimp.com.
Something else for Microsoft to fix .........maybe .......hopefully ........someday.
did she get a plain text copy? If so, that is "normal" when there is a winmail.dat file.
Yes she did. I didn't realize that this new Microsoft feature would kill embedded links as well as attachments.
it's not a new feature, it's a bug, but that is a side effect of seeing the winmail.dat file.
http://www.businessinsider.com/10-bugs-that-became-features-2012-11?op=1
it's definitely a bug because of the data loss (even though it not really lost, just hidden and difficult to access).
This probably should be in a separate thread, but since the theme here is Microsoft's incompetence..........
It just keeps getting better and better. On a hunch I went into Outlook.com and looked at the Blocked Senders list. I discovered dozens of e-mail addresses that I never would have blocked and whose e-mails I want to receive. I have no idea when/how these addresses were blocked. This might be a consequence of Microsoft moving Outlook.com to an Exchange-based platform, in which case it could be of a piece with the winmail.dat debacle.
There were also a lot of mysterious e-mail addresses in the Safe Senders list, but at least this screw-up doesn't block e-mails.
they probably came over from the old server - the old server added addresses to the list, some of which were not valid (happened to me more than once - it was probably more that it made it easier to add them when deleting messages and I didn't pay attention). The only other way is is you accidently did it or an antivirus or security add-in did it. My oldest hotmail account has a very long list of blocked addresses and for about the last 15 years, I only use it for testing and let the built in filters deal with spam.
Yet another bug to report to Microsoft. Starting a few days ago, "Mystery" contact records appeared in Outlook 2016 and Outlook.com. They contain nothing but a phone number. These appear to be fragments of valid contact records. I can't see any pattern of similarity among the full contact records. They were created at various times on Wednesday, 4/12 (The day after Patch Tuesday).
Do you sync with a smartphone?
When you create contacts, try adding something - even just a space to the address field. This seems to fix some issues, especially when you sync with a phone.
Any update on when (or if) Microsoft is going to fix this bug?
Do you have a recommendation for another "ecosystem" that will sync e-mail/contacts/calendar between Win10 desktop, web and Android (including phonebook)?
eM client does a pretty good job with gmail and outlook.com calendar & contacts. It's what i'd use if i didn't use Outlook.
Any update yet on when (or if) Microsoft is going to fix this bug?
Are they getting even a little bit embarrassed?
Should be soon - both this bug and the 'outlook.com hogs the reply address' bug are in upcoming builds. If not in 8067 (coming out now to current channel), then 8216 (coming soon to insider fast). I have 8117 and will check it.
Hallelujah! (Although I'm keeping my salt shaker handy.)
Do you know if they will be able to repair the damaged formatting in the Contact records?
I don't know about the formatting, but am guessing no. Syncing outlook to outlook.com shouldn't affect the formatting, but syncing with smartphone apps can and that is out of their control.
I sync from Outlook.com to Outlook 2016 (which is bidirectional) and from Outlook.com to Outlook for Android (which is one-way, to the phone). I don't see any way the smartphone could have mangled the Contacts in Outlook 2016. The formatting problems I've encountered are described earlier in this thread.
I updated to 8067 last night but it didn't fix the winmail bug.
Then that fix will be in an upcoming build - others have confirmed the reply bug fix is in 8067.
I haven't heard yet - will ask about it again though.
I finally got around to rebuilding Outlook 2016 using a second Profile. No change on the Winmail.dat bug and OffCAT is still spewing errors.
Any update from Microsoft? Hope springs eternal.
Thank you for the article. This has become a nightmare trying to figure out how to fix this. My boss is the only one who gets these wind dat files and he is getting very upset about it. I do not want to work out of Outlook.com all the time as I do not care for it.
I cannot seem to fix mine and was wondering if you could help me in further detail.
Microsoft is investigating it but I don't have an ETA for a fix. For new messages, don't use the To button or autocomplete - go into contacts, select his contact then click EMail button in ribbon. If the problem occurs on replies, try creating the new message from contacts then copy the address and paste into the To field of the reply.