Jade,
It is not uncommon. It is how almost all products POST to API's and require / demand HTTPS!
No customer should run a mail server without HTTPS enabled and required!
Also, most synchronization protocols for mail used over the Internet are the same way. It is for that reason HTTPS / TLS etc. should be enabled.
Tim
Tim Uzzanti
CEO
SmarterTools Inc.
www.smartertools.com