winmail.dat

Question

I sent a spreadsheet via email and the recipient cannot open it and it says that the file is winmail.dat - what does that mean and how do you open it?

Answer 1

See https://support.microsoft.com/en-us/help/278061/email-received-from-a-sender-using-outlook-includes-a-winmail-dat-atta

That really shouldn't happen when sending a spreadsheet.  Did you save the spreadsheet as a *.xls or *.xlsx file and then attach it to the email or did you try to copy and paste it into your email?  You should save the file and attach it; don't use copy/paste.

If all else fails, save the file on your computer.  Then right-click it and select "Send to > Compressed (zipped) folder."  Make a note of where the *.zip file is saved and then attach that file to your email.

More reading:

How to Prevent Winmail.dat Attachments from Being Sent in Outlook:  https://www.lifewire.com/prevent-sending-winmail-dat-attachments-1173717

What is the WinMail.dat file attached to my incoming emails?  http://www.pchell.com/support/winmaildat.shtml

There is a program that can actually read winmail.dat files (although I don't know what it would do for spreadsheets).  It was developed for Windows 95 and I have no idea whether it will work on Windows 7 (32-bit version, probably; 64-bit version, probably not).  Although the website indicates that it was updated as recently as 2016, there's no further information about which versions of Windows it supports.  http://www.fentun.com/