If you are using IMAP, then the e-mails are saved on the server. If you are using POP, then the e-mails are not saved on the server.

If you are using POP, then switch to IMAP: Switch from POP to IMAP account

rbottari sent me the following message privately:

Hello i deleted email account reinstalled thunderbird again when i go to server settings the is no box to check to save email on server?yes im using imap

Please always reply in the forum.

The difference between POP and IMAP

With POP, all the e-mails from the server get sent to Thunderbird, Thunderbird saves those e-mails on your computer, then tells the server to delete those mails from the server. Unless you set an option in Thunderbird to not tell the server to delete the e-mails.

With IMAP, the e-mails are kept on the e-mail server. Thunderbird continually communicates with the server to show the e-mails on the server, but doesn't necessarily save them on your computer. You can tell Thunderbird to also save the e-mails on your computer.

When using multiple devices to access the same e-mail, the only way to keep the e-mails synchronized between the devices is to use IMAP.

Another thing to remember, is that anything in the "Local Folders" in Thunderbird are only on your computer.