I looked in the tb code and found this: mail.server.default.send_client_info If you set it false using the "config editor" in tb, it should stop tb from ever sending the ID command (again, restart tb is recommended). This will affect all your accounts but doubtful that other servers will care either. If it does cause problem for others, it's possible to define new prefs that are server specific. Let me know if this works. P/S: Yes, I know what you mean. Had a similar problem with my ISP email, charter.
Bug 1571655 Comment 11 Edit History
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I looked in the tb code and found this: mail.server.default.send_client_info If you set it false using the "config editor" in tb, it should stop tb from ever sending the ID command (again, restart tb is recommended). This will affect all your accounts but doubtful that other servers will care either. If it does cause problem for others, it's possible to define new prefs that are server specific. Let me know if this works. P/S: Yes, I know what you mean. Had a similar problem with my ISP email, charter. Edit: But there seems to be a lot more complaints about this at bt forum than there were with my problem with Charter: https://community.bt.com/t5/Email/unrecognised-imap-4-command-when-using-thunderbird/m-p/1959282