I may complete that I receive the message: "L’envoi du message a échoué. Le pair utilise une version non gérée du protocole de sécurité. La configuration liée à mailhost..... doit être corrigée"

Please clarify what product you need help with. You posted your original question about the new release 78.4.0. in the Firefox for iOS forum for mobile devices. Firefox 78.4.0 is the latest Firefox ESR (Extended Support Release) version. Your Question "More system details" shows a desktop Firefox version 82 on macOS 10.14.

If possible, also post your replies in English.

I may complete that I receive the message: "L’envoi du message a échoué. Le pair utilise une version non gérée du protocole de sécurité. La configuration liée à mailhost..... doit être corrigée"

From Google Translate (French detected)

"Failed to send message. The peer is using an unmanaged version of the security protocol. The configuration linked to mailhost ..... must be corrected

Are you asking about the new Thunderbird mail program version 78.4.0?

Moved to Thunderbird forum.

alain.finkel, You marked my previous reply as the solution. Can you tell us what solved the problem ... or do you still need help?

Hi,

I re installed the previous version of Thunderbird 68.12 and it is now ok. The problem came from my server of mails which is not compatible with the last version of Thunderbird because the security protocols are not the same. Thank for your help.

Alain

Hi, I re installed the previous version of Thunderbird 68.12 and it is now ok. The problem came from my server of mails which is not compatible with the last version of Thunderbird because the security protocols are not the same. Thank for your help. Alain

Thanks for letting us know how you fixed the problem. I marked your reply that you got it working by reinstalling Thunderbird 68.12 as the solution.

If you want to try Thunderbird 78 again, either now or in the future, see the Thunderbird 78 FAQ article section, After upgrading to Thunderbird 78, I cannot get or send email messages, which explains that One reason why this might happen is when your email provider is using outdated security protocols. and goes on to explain how to temporarilychange the security.tls.version.min preference to 1 in the Config Editor, to see if this is in fact the problem.