you have an email address with non ascii characters before the @, as this has never been supported it is not a change, so I assume you have a new contact.

I have the same problem. It occurred out of the blue today. Addresses that I have used frequently for a long time are suddenly being blocked. Please reply ASAP.

Mon problème c'est que je ne sais pas de quel adresse il s'agit. J'ai corrigé dans une adresse groupée que je venais de créer, et à partir de cela j'ai eu le message, mais cela continue. Mes messages partent sans problème. mais ce message s'affiche tout le temps et c'est gênant.

I have this problem today as well. I added a new contact to a mailing list and suddenly couldn't send mail to the list. I have removed the email but continue to have the problem. Help! Mail needs to go out.

I have checked every address, and there are no non-ASCII characters in any of them.

I have the same problem. I reported it several days ago and am desperate for a solution. Somebody, please help!

Yes please help. I have the same problem. I have backed up Thunderbird, completly desinstalled thunderbird with Revo Uninstaller and reloaded Thunderbird. I still have the same problem.

Hi everyone, I have exactly the same problem today (April 22, 2020) all of a sudden on my French Thunderbird: "Des caractères non ASCII sont présents dans la partie locale de l’adresse électronique du destinataire . Ceci n’est pas encore pris en charge. Veuillez modifier cette adresse puis réessayer," whici is the French for "There are non-ASCII characters in the local part of the recipient address. This is not yet supported . Please change this address and try again." I've tried to get read all of the accents (and even Thai charaters) in some names in the addresses, i.e. in some first names and surnames), and I have checked, there no non-ASCII letters in the email addresses proper, in the email I want to send. I've never had this problem before, and it's been years I have been using Thunderbird. So I presume that this is probably due to a bug in a very recent update. Help, please!

I have the same problem e-mails despatched through a mailing list OK until this week when I got the 'there are non-ASCII characters ...' error message. - Checked every email address on list no suspicious characters. - Rebuilt the entire mailing list as a new list - same problem. - Copied every email address one at a time from the Mailing List to a word program & studied each address but found no suspicious characters. - Sent new (non Mailing List) e-mails & copied to them 20, 30, 40 addresses one at a time from the problem Mailing List - this email sent OK with no problems.

It seems therefore that perhaps a recent update has caused a bug in the Mailing List section of the program. Any ideas from the support team?

Thank you for your post! I am still waiting for a solution as well. With a number of us reporting this problem it has to be something in the system and not in our lists!

Is everyone having this party using a mailing list to send the mails that have an issue? Does the mailing list name contain a non ascii character.

This is the bug report to finally remove the limitation on local parts. https://bugzilla.mozilla.org/show_bug.cgi?id=1563891

Looks like the powers that be have decided "It would be nice to tackle one day, but more as a part of a drive for email l18n."

Matt, thank you for your reply. I have NO non ASCII characters in my list--have been using this list for over a year with no problems. Suddenly there is a problem. What changed? And how can it be resolved as it appears from your response above that "the powers that be" have decided no solution will be happening right now. Something must have changed in the system (I am not a tech person so this is probably not the right term)in the last week for this to suddenly be happening to a number of people. What can we do? Any suggestions? thank you!

I experience this error when sending to a mail list that has NO non-ASCII characters in any of the addresses. It's basically a show-stopper for me.

Same problem. I can mail to each of the addresses on a list individually with no problem, but if I try to use the list, I get the "non-ASCII Characters" error.

It is worse for me as I do not know were it comes from. And I have non stop that advertisement that pops up all the time and is a real bother.

I have the same problem. No nwe addresses added. So I assume it is a bug in the update.

Pleaser repair the bug, it is a eal nuisance to have to message pop up every few seconds

Yes, please get this fixed ASAP!!! It's preventing me from using Thunderbird except for emails to individuals.

As so many users have said, can this blip not be fixed soon. I have a large multiple maiing to despatch tomorrow and the thought of entering a couple of hundred addresses again into the address box is a nightmare. It all went perfectly well up until last week but now do I have to do this every time for a multiple mailing?