Outlook sending Winmail.dat Attachments

By: standss , Jul 5th, 2011

Recently we have had several customers mentioning that there attachments are removed on the recipient end and instead a Winmail.dat file is found attached. Many have contacted us asking if this was due to one of our Outlook addins so we decided to do some research on this. NO!

It turns out that this is a long standing problem between Outlook and Internet email.

Outlook uses an email format that Outlook and Exchange (and MANY other email clients like gmail) can recognize. However some email clients (including unfortunately the IPhone and IPad mail clients) have problems displaying these emails properly.

If you send a email with Attachment to a user of an email program that has problems with Outlook emails, then the recipient gets a plain text message and an attachment called winmail.dat. Any attachment that you might have sent with the email is encased in the winmail.dat attachment.

For those who receive a Winmail.dat file, you will need a tool/utility in order to extract the attachments from the Winmail.dat file (you can easily find a free tool using Google Search).

6 Replies to “Outlook sending Winmail.dat Attachments”

  1. Interesting. Not what I’ve experienced at all. If I add-in, for example, QuickFile, I get customers complaining I am sending winmail.dat files on every email they receive, regardless of an attachment or not. I had to disable it and haven’t upgraded as a result. No issue with email merge. I really wish there was a solution for this. I would love to use your add-ins. I can not imagine I’m the only one. IMHO this is worth checking into very thoroughly.

  2. Unfortunately, I think everyone knows what you published above. The issue is preventing the problem from happening. There are other posts that talk about unchecking “Send in Rich Text Format” but that doesn’t always work. Is there a registry change to fix this or something else. This has been going on for years and I think the one consistent thing is Outlook and Apple devices. I can send an email from Outlook to someone that has a Gmail account and is reading it on an iPhone or iPad. They get winmail.dat. If I go to the MSN site and create the email using my browser and send the same attachement, no problem. The attachement arrives as it should. After all of these years, somebody should fix this so people don’t have to go to another email client for this group of people and use Outlook for the other group. Frustrating!

  3. Hello Tom,

    Did you have a HTML signature in the email which you send out to the recipients?

    If you did have a HTML signature, then the Winmail.dat file would have been the result of this.

  4. Thanks for addressing this issue. I was composing emails in plain text format, but had the format set to convert rich text to plain text; however, Outlook defaulted to let the program decide the format to send my email signature, which created a HTML link. Hopefully, I solved the problem by creathing a plain text email signature. Maybe the price to pay for virus protection.

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