If you are using a standard email client, it doesn't use HTTPS . If the email server you are connecting to supports encryption, it will be a different port and a different protocol.
The protocols used for email are SMTP for sending email (port 25, nothing is encrypted by default) and IMAP or POP for retrieving email (port 143 and 110 respectively, both are not encrypted).
The protocols have been updated to support encryption and are typically on a different port (however SMTP supports something called STARTTLS that can upgrade a connection to use encryption). Secure IMAP is on port 993 and Secure POP is on port 995.
Protecting your email from prying eyes is a little more involved if you are using an email client. However it is better to check your email using webmail over an HTTPS connection if you are on a shared public network.
Aren't these features fairly commonplace these days? (I use two mail servers, one of them is Gmail) and they both support TLS, actually, they even refuse me to connect in plain text.