Can I redirect mail.mydomain.com to customzied webmail login page?

Can I redirect mail.mydomain.com to customzied webmail login page?

I'm a new mail user, so I'm sorry if this is addressed somewhere.  Can I have users go to mail.mydomain.com to sign into webmail, rather than going to mail.zoho.com? I realize I can forward the domain, but I wasn't sure if I could have a 'custom' webmail signin page