How to create a group from an email in Outlook.com

Unfortunately there doesn't appear to be a way to do this directly.

This is the fastest way I found to do it in Gmail.

1. Click "show details" to display the entire To: field
2. Copy all of the e-mail addresses shown there
3. Change to "Contacts" and select "New Group"
4. Click on the group name to display it
5. Click the button which says Add to "<groupname>". This will open a simple text area
6. Paste the e-mail addresses you copied into the text area

If any of the e-mail addresses are already in your contacts they'll just be added to the group.

It certainly does seem like Google is missing an opportunity here, though.

I don't see a way to add them all in one, but you can add a whole domain (the part of an email address after the @ sign). If you import all your contacts they will automatically be a part of the safe senders list.