re :Why when i delete email in my gmx account does it also delete emails from my computer.

This sounds like you have set up an IMAP mail account in Thunderbird for the gmx account.

IMAP shows a virtual view of whatever is on the server by synchronising subscribed imap folders with server.

So the folders in an IMAP mail account are really one and the same as the server.

If you delete an email via webmail or via anything that removes off the server, eg: imap mail accounts on other devices or Thunderbird then Thunderbird imap will synchronise with server and show exactly what is on server.

This is not a Thunderbird quirk, it is how all imap mail accounts work.

re :And how do i stop thunderbird from automatically downloading my email

Imap accounts work by synchronising folders to show what is on server.

You can choose to only download headers. When you select to view an email, it is downloaded from server and stored in a temporary file on your computer to facilitate viewing. It is not downloaded and stored in Thunderbird. All emails are stored on the server. You cannot read the contents of emails when in offline mode because there is no connection with server to download them. If you delete and email then it will get deleted off the server as well when folders synchronise.

You can choose to download full messages for all or some folders. The downloaded emails are stored in Thunderbird profile folders in text mbox files. This means you can open and read them even in Offline mode. The emails are still stored on the server, but it also means you can exit Thunderbird and perform a backup of Profile Folder to eg: external backup drive, so you also have a copy.

You can also copy downloaded emails into 'Local Folders' mail account. If you can read emails in 'Local Folders' mail account whilst in Offline mode, then you have a copy outside of your imap mail account. 'Local Folders' mail account folders do not synchronise with anything.

I would suggest you read the information at the following link to understand how IMAP account work and how you can choose to fully download emails and choose which folders to fully download or only headers.

• https://support.mozilla.org/en-US/kb/imap-synchronization

You could choose to start Thunderbird in 'Offline Mode': Working in offline mode will not synchronise with server or download anything untill you go into online mode. You can set to follow or not follow detected online state and choose options here:

• 'Menu icon' > 'Options' > 'Options' > 'Advanced' > 'Network & Disc space' tab
• Configure offline settings
• click on 'Offline...' button
• make selections and click on all the OK's.

In Account Settings: You can choose whether to check for New messages at startup or to allow immediate server notifications when new messages arrive (server auto synchronises regardless of how frequently you check for mail). You can also set how frequently to check for them. To access where this is set up:

• Right click on mail account in Folder Pane and select 'Settings'
• select 'Server settings' for the imap mail account.
• After making changes, click on OK

I would advise you exit and restart Thunderbird to ensure all is using the new changes.

There is another option. It is called POP. You usually have to select if you want to download using pop and this is done in the webmail account before creating a pop mail account in an email client. Pop mail accounts can only access and download from server Inbox. They do not have any access to any other server folder. They usually auto delete copy off server after allowing download, but you can set Thunderbird to tell the server to keep messages on server. Pop accounts use entirely different server settings. You cannot simply swap an imap into a pop or vice cersa. They need to be created separately. Pop accounts store emails in Thunderbird. You can delete off webmail and it will not effect whatever is currently in a Pop mail account. It is advised you create regular backups as usually the only copy is on your computer.