Ok, I found the solution. You cannot have spaces in the recent upgrade.

List name will not work

Listname does work

There is a thread on this if you search "email lists." For me it was not a problem in 31, only started with 31.1, but others had it starting with 31

Correct, this is a regression and has been reported as Bug #1060901. If you have an account on Bugzilla, please consider voting for that issue.

Several other people have sent in the same support request as you, noting this happened after they upgraded to version 31.1.

The exact error message is: XXXX is not a valid e-mail address because it is not of the form user@host. You must correct it before sending the e-mail.

This happens in Thunderbird 31.1.0 when your mailing list description includes several words separated by spaces.

Although not ideal, these workarounds should let you use your mailing lists until a proper fix is implemented:

• While composing an email open the address book and select the list you are trying to send to, highlight all the names in the list and drag them to the To: box. This uses your existing data without modifying it.

• Replacing the blanks " " between the words in such lists' descriptions with an underscore "_". This requires modifying your mailing list(s) description(s).

• Downgrade to a previous version and disable automatic updates (Windows)

About automatic updates

Automatic updates are the default in Windows.

You can customize such behavior, however, it's under Tools > Options > Advanced > Update.

My suggestion would be to set it to Check for updates, but let me choose wether to install them., specially if you depend on email for critical / important business or personal matters.

Wait just a minute here.... I also discovered this list problem but, in preparation to create the parts intended for further diagnosis, I've discovered another list problem. Here's the procedure.

I created a new contact "test1", for intended use in this list testing. This was a very minimal contact. First name=test1, nickname=test1, and my own email address. Then, I created 3 more contacts the same way. But they're test2, test3, and test4. All 4 have the same email address.

I checked the contact entries, and all looked good.

Then, I created a new list named "test". And, as you might expect, populated its member inventory with the 4 contacts I just described. Finally, I checked the new list, and it appeared just as I would have expected. Including the 4 member contacts test1, test2, test3, test4.

Through testing I discovered that using this "test" list returned email to me from "test4", "test4", "test4", and "test4.". WTF !

So, I returned to the "test" list, and all member contacts specifications for the "test" list had been changed to "test4". So, I deleted all the "test4" list contacts, and rebuilt the contacts list again as "test1", "test2", "test3", "test4". I verified the creation again, and closed the address book form.

But, this time, instead of testing the "test" list, I simply reopened the address book form to review the "test" list again. To my surprise, all 4 of the member contacts for the "test" list had been changed to "test4". Just as I had experienced in the first test.

So, give it a try. See of you can build a "test" list containing the "test1-Test4" contacts, without this unsolicited change.

@gmak when replying to a support request here, if you found another problem please do not mix them. Create a new post instead or file a bug report. This makes the best use of everyone's time and makes it easier to read / address requests. Thank you!

First, I'm sorry for the incident mix. I know that rule well from every other similar forum, but I just wasn't thinking, and the relevance quotient did seem quite high.

Also, I was asked for a message identifier. I'm relatively unfamiliar with this forum, but I'll try to add a screen shot reference. However, I'll also compose the message text below , in the event that the image reference fails.

"caic Friends <"CAIC Friends"> is not a valid e-mail address because it is not of the form user@host. You must correct it before sending the e-mail."

Of course, "caic friends" is the list name.

Clarification alert:

This message described, addresses the list entry failure only(as many others have mentioned). The list compose problem I first described above(and incorrectly combined incidents), using the "test1, test2.", etc., produces no error message. Just incorrect output.

Also, I'm not suggesting that the error I wrote about on 9/4 @ 17:24 was caused by my upgrade to v31.1.0. I can't know because I'd never created any list entries for my Tbird implementation . All the list entries I have were auto-created via import from MS OE6 during my initial migration.

Thanks.