Windows 10 reached EOS (end of support) on October 14, 2025. If you are on Windows 10, see this article.

Search Support

Avoid support scams. We will never ask you to call or text a phone number or share personal information. Please report suspicious activity using the “Report Abuse” option.

Learn More
Open

Mozilla Thunderbird ESR; Authentication error connecting to server imap.gmail.com

teravainendata

Hi, When i start the TB-client on a win10 desctop there will be an Authentication error connecting to server imap.gmail.com.

from Google: 400. An error has occurred, The server cannot process the request because its format is incorrect. The request should not be made again. Unfortunately, we don't know more than that!

It still seems like the email arrives to the gmail account. But it turns out that the email doesn't always arrive via sync. Do you see any problems with the TB and gmail connection?

For the moment I don't know the Thunderbird version, I will be back.

TIA, /Leo

Hi, When i start the TB-client on a win10 desctop there will be an Authentication error connecting to server imap.gmail.com. from Google: 400. An error has occurred, The server cannot process the request because its format is incorrect. The request should not be made again. Unfortunately, we don't know more than that! It still seems like the email arrives to the gmail account. But it turns out that the email doesn't always arrive via sync. Do you see any problems with the TB and gmail connection? For the moment I don't know the Thunderbird version, I will be back. TIA, /Leo
Attached screenshots

All Replies (1)

Make sure cookies are enabled. TB menu > Settings > Privacy & Security > Privacy > Web Content > Accept cookies... After logging in, you should be able to uncheck it.

Ask a question

You must log in to your account to reply to posts. Please start a new question, if you do not have an account yet.