How do I specify IMAP (and only IMAP) protocol?

How do I specify which protocol I want tu use with em Client: IMAP or SMTP? The help system inside my em Client says that em Client supportes both IMAP and SMTP and that’s great but it does not tell me how to specify either one of these protocols. I would like to use IMAP with em Client so that my emails remain on my email server. When I look at “Tools>>Accounts…” and check the IMAP tab and SMTP tab I see entries for both that name a host server (mail20.dotsterhost.com) and ports (993 for IMAP, 587 for SMTP).
How do I tell em Client to use only IMAP?

Actually eM Client uses the SMTP protocol only for sending messages to a mail server. For receiving messages eM Client can use either the Post Office Protocol (POP) or the Internet Message Access Protocol IMAP.
Are you sure, that you do not want to send messages?