Custom URL for Office 365 Webmail

Setup a CNAME record pointing mail to mail.office365.com.

Your users are probably used to going to "mail.yourcompany.com" to get their web mail. With Office 365, the standard URLs are portal.office365.com or login.onmicrosoft.com, which takes you to a list of office applications, including mail.

You can direct your users directly to Office 365 webmail by using mail.office365.com. Or you can setup a CNAME that points mail to mail.office365.com.

Now anyone going to mail.yourcompany.com gets sent to mail.office365.com which is the Office 365's webmail.