Hi, I am using Firefox to open my different mail boxes from : yahoo.fr or orange.fr or laposte.net. Usually everything are going OK and I can read the attached files except the one sent by my friend from England. Sorry for my English but you may have understood I am french (nobody is perfect). Well, I am using windows 11, he is using windows 11 ; I am using Firefox but he is using mainly Microsoft Outlook. All his attachment are coded as winmail.dat and I can't open them. If I use Microsoft Edge it's not much better. When he uses Chrome and Gmail it's perfect and I can open his attachment with Firefox. He is a computer man, programmer, and his Outlook seems to be correctly set and he doesn't understand the problem or what's happening. I am not the only one in that case. It seems it's an Outlook setting specific problem according to Microsoft. Clearly, I don't want to give up with Firefox. Does it exist an add-on or extension for Firefox which could solve this difficulty ? or a decoder add-on ? It seems there is at least one for Thunderbird but 6 yo... Would it run under Firefox even it's specific ? For fun I should try Firefox with Linux just to see if Linux is better at decoding winmail.dat attachments. Thanks for any help, setting or specific add-on you can provide me. Richard.