Hello,

If I understand correctly, your GMail is active in Thunderbird along with you ISP mail...

Go to preferences, for the account to modify, choose (isp or GMail)...

Untick check for messages on launch... and download messages auto...NOT auto.

You can also choose to leave a copy on the server for GMail if desired, so that all mail collects there for backup, ease of use, etc.

Good Luck,

Hope this Helps,

CF

Post Script>> Now in thunderbird your result should be that upon launch, isp downloads current messages, and DOES not on GMail automatically..., To check Gmail, use side button drop down check, and choose only GMail account.