You use Outlook and send emails with attachments. A recipient of an email tells you that he cannot read the attachment: instead of the attachment there is a file named winmail.dat that he cannot open. The recipient of your email is probably not using Outlook but another email client. It is interesting that if you send an email to another recipient who uses the same email client as the first, same version, he can see and read the attachment correctly.
The first consideration is that the problem “is in you” and not your mail recipients. You need to fix the problem on your Outlook.
Solution 1: send emails as Html
For the first solution you will find hundreds of articles on the internet, we report it here for completeness. You need to set Outlook to send emails in HTML format. In Outlook:
File -> Options
Select “Mail” on the left. You have to make 2 variations.
- Under the Compose messages section, change the “Compose messages in this format” dropdown box to HTML
- In the “When sending messages in Rich Text format to Internet recipients”, ensure you select either Convert to HTML format
Outlook from several versions already has these default settings, so you didn’t need to make these changes. In fact, if that were the problem, it would not explain how some of your recipients are successfully receiving attachments. You haven’t solved the problem.
The definitive solution. The problem of self-completion
If you have correctly configured Outlook as above, here is the definitive solution. The problem is in the auto-completion of the email address. The recipients of your emails who have this problem are surely in memory in the Outlook auto-completion. Auto-completion is that function that is activated while you write the email address in a new email: while you type the recipient’s address, a drop-down menu appears showing the last used addresses. If you use the proposed address, your recipient will receive the winmail.dat file.
If, on the other hand, you write the email address without selecting the address proposed by the auto-completion, your recipient will receive the right attachment.
Let’s recap. The winmail.dat problem affects only some of your recipients; they are recipients who do not use Outlook and have the e-mail address stored in the Outlook memory which appears with auto-completion.