I am using Thunderbird to transfer emails from my main Gmail account to another gmail account as a back up when my main email account storage is full. So whe the backup gmail account is also full so I want to unlink it from Thunderbird without deleting the server / backup account messages. How do I do that? I tried simply deleting from the Thunderbird account but it deletes from the back up account as well. Any ideas - hope I have explained this properly