DNS: redirect webmail.domain.com to mail.office365.com fails if user or auto-complete jumps to https://mail.office365.com

Howdy, 


I have setup the organizations externally hosted DNS (that has to be external for other needs) to point with a CNAME record to mail.office365.com, as per the instructions I've read from Microsoft, and that works, and lands them ultimately on https://login.microsoftonline.com, where they can use their custom domain credentials to login correctly.


I have an issue where users are either accidentally or via auto complete, typing "https://", which then goes out to "https://mail.office365.com", but this then re-directs to a non-working site (non-organization login page) such as "live.com" or "outlook.com" where they can not use their custom domain name organizational logins, they get errors about name/password not valid if they try, and this is creating great confusion for the users.

It seems to me, that since they are actually getting a landing page of "https://login.microsoftonline.com" , which works correctly, perhaps instead of the CNAME record pointing to mail.office365.com., but instead to "login.microsoftonline.com.", which seems to work correctly with either the "http" or "https", as they both land on "https://login.microsoftonline.com", which then works correctly.


I'm concerned however, as this is not what Microsoft instructs us to do, and if they someday change the landing page, thinking that mail.office365.com will alway re-direct to their desired landing page, if this changes someday, then perhaps "login.microsoftonline.com"  mail fail someday and cause more problems.


I'm not sure if this is a safe change to make, nor why Microsoft has "http://mail.office365.com" and "https://mail.office365.com" goes to two different pages instead of the same one. I would imagine this also creates confusion and problems for many organizations.


Thanks, 


Daniel