re :''And only download when I open up Mozilla. '' You need to have Thunderbird running and in online mode in order to access server and download. Are you using IMAP or POP mail accounts? Do you use an Anti-Virus pram to scan incoming emails? If yes, then this can cause some delay, but not usually as long as you mention. You could access the AV and tell it to not scan Thunderbird files and folders and stop scanning incoming/outgoing mail. It is possible you have an overlarge Inbox or other folders which are taking a long time to synchronise. If you have not been compacting on a regular basis they may be larger than you think as they could contain a load of 'marked as deleted' emails. As it is unknown if there is any corruption on the Inbox, I suggest you do the following on your mail account Inbox and other folders as advised. Inbox: * Move all good wanted emails into other suitable folders for organising and storage. * Delete any emails you do not want. When Inbox is empty: * Right click on Inbox and select 'Compact' * Right click on 'Drafts' folder and select 'Compact' * Right click on 'Junk / Spam' folder and selct 'Empty Junk' * Right click on 'Junk / spam' folder and select 'Compact' * Right click on 'Deleted / Trash ' folder and select 'Empty Deleted' When you have finished doing the above, exit Thunderbird. Allow a little time for background processes to complete. Start Thunderbird. Please report back on performance results.