Where is option to leave email on server?

[Gary]

@Bastus

deleting emails from the client on the desktop does not delete them from the server.

That is true only for POP3, and dependent on your having specified not to delete the message from the server.

For IMAP, if you delete the message in eM Client, you delete it from the server. That is because IMAP is simply a view of what is on the server, so changing something in the email client means it is simultaneously changed on the server.