If all recipients are in your address book (in Contacts or GAL) or the address is in the display name (either the address only or in this format: "Diane (diane@domain.com)" ) you can copy from the To and CC fields in any version of Outlook. Outlook will resolve the names to the contacts.

You can use any list of email addresses to create a DL (or Contact Group), including from Excel or a custom view in Outlook (with only the display name and email address visible.) The only requirement is that each member's information needs to be delimited with a semi-colon or paragraph mark (one name and address per line). If there is not a display name, the address will be used for the display name in the finished DL.

poremsky <me@gmail.domain.com>
Diane Poremsky <me@domain.com>; <diane@domain.com>;

Which Group command to use?

Outlook, when used with Office 365 Exchange accounts, has two types of Groups available. You need to select Contact Group, not Group. The Group command will create and Office 365 Group, which is a special type of mailbox.

From the New Items button, you need to select More Items > Contact Group.

In the Contacts module, use New Contact Group.

Create a Contact Group from an Email

If you use Outlook 2010 or newer, you can hit Reply All then copy the addresses from the To and CC fields.

Paste into the members field of a Contact Group form (DL).

Create a DL (Contact Group) from a List of Addresses

This method is only needed if you use older versions of Outlook.

While you can get the addresses from any semi-colon delimited or one address per line list, this page was originally written to help people who wanted to create a DL from addresses in a message they were CC'd on. The instructions to create the DL once you have the list of addresses is below.

To get the addresses from the Internet header

1. Right click on the message.
2. Choose Message Options
3. Click in the header field of the Message options dialog and press Ctrl+A to select all, Ctrl+C to copy.
4. Close the dialog.
5. Open a new message form and paste the header into it. I press Ctrl+A to select the signature then Ctrl+V to paste over it.
6. Delete the content below the addresses and above it.
7. Remove the text "To:" "CC:" and "From:"
8. Use Find and Replace to replace the commas with semi-colons and tabs (^t) with a space.
   If a name and corresponding address are on different lines, backspace to remove the paragraph mark. If you aren't sure, Ctrl+Shift+8 to toggle marks on and off. Or use Find and replace to replace paragraph marks (^p) with spaces.
9. Copy the prepared addresses. (Ctrl+A to select all, Ctrl+C to copy)

Create the Distribution list

These screenshots are from Outlook 2010 but the screens look similar in other versions.

Outlook 2010 and newer

1. Open a new Contact Group form
2. Click on Add Members in the ribbon and select either From Outlook Contacts or From Address book
   
3. Click in the Members field (at the bottom) (2 in the screenshot below)
4. Paste (Ctrl+V) the address list into the field
5. Click OK to add them to the Contact Group. (3 in the screenshot)
   
6. Enter a name for your group in the Name field then click Save & Close.

Outlook 2007 and older
The steps to do this in the older versions of Outlook are basically the same but the labels may have changed.

1. Open a new distribution list form
2. Click on Select Members
3. Click in the Members field (at the bottom)
4. Paste (Ctrl+V) the address list into the Members field
5. Click Ok to add the names to the DL
6. Enter a name for your list then click Save & close.

Video Tutorial

This video tutorial shows you how to get addresses from the header of a message in your Inbox and create the distribution list.