At this time, Xpress is only able to send Alarm E-mail via an SMTP mail server without any security on the login for the server. (Server must not require username and password) It does not support SSL or TLS servers at this time. The current release as of the entry of this FAQ is 4.1
For 2.1.6 the e-mail address must not include dashes in the name. "example@my-email" will fail to validate and appear in red when entered. If you are not using 2.1.6 and the address validates with a dash (it stays black when entered) it should work.
There is no available timeframe for making any changes to the functionality of Xpress that would effect this feature.
Updated 101716 for affected versions.