How can I open a winmail.dat file on an iPhone? Can I use the files app on the iPhone? And what is this file, why not just make it a pdf?
A winmail.dat file contains rich text format information about an email created by Microsoft Outlook. It dates back to a time when Microsoft couldn’t be bothered to follow Internet standards for email.
You can try opening it in Microsoft Word on a Mac or PC (which will result in a lot of garbage and occasionally some useful information. Or you can purchase a utility in the App Store to open it. Last time I checked there were several, most costing $0.99.
The easiest solution would be to ask the sender to resend the email in plain text, but no one I know ever did that.
I was asked to open these occasionally by one of my users. I can’t remember a single time when it contained anything important. IMO, they can be ignored.
Try TNEF’s enough on the App Store. Free. I’ve used the Mac version for years.
2016 blog post on how to use it here.