Gmail keeps a record archive of all your emails in the 'All Mail' folder. If you subscribe to see the 'All Mail' folder then it will download what could be a huge file of everything. If the 'All Mail' folder on the server has more in it than you are aware of, it will use up quota.

If you delete emails from a folder eg: Inbox, then this will not necessarilly delete those emails from the 'All Mail' folder.

• https://support.google.com/mail/answer/78755?hl=en

If you delete an email from the 'All Mail' folder then it will be deleted from any folder it displays in, as all labels are removed.

I can advise you check two things. Logon to gmail webmail account using a browser and access the 'All Mail' folder. You may discover loads of emails you do not want to keep or thought were deleted, but they are still lurking in the 'All Mail ' folder using up your quota.

You could choose to delete some of those old mail messages you thought had already been deleted.

In Thunderbird gmail mail account, which I'm assuming you have set up as imap: Do not subscribe to see the 'All Mail' folder then it will not download all of those emails, but they will stay availbale on the server. More info on gmail 'All Mail' - scroll down to see 'All Mail' section:

• http://kb.mozillazine.org/Using_Gmail_with_Thunderbird_and_Mozilla_Suite

See additional info: https://support.mozilla.org/en-US/kb/thunderbird-and-gmail

Thank you Toad-Hall, I've been playing around with Thunderbird and figured being able to sort emails is much easier than with Gmail. I simply starred all the emails that I wanted to keep in all my folders, then went to the All Mail folder in Thunderbird and brought all of the starred ones to the top and selected the rest of the emails not starred. Then I proceeded to delete them all permanently from both Thunderbird and the server (which took some time to figure out). So far, I really enjoy Thunderbird! :)