Include the alias in the email body if it's included in the "To:" field

[nguyenkims]

When an email is sent to a mailing list that an alias is part of, the To: field is the mailing list address and user can't know to what alias the email is sent to.

Another possible scenario is when an alias is "leaked" and now receives spams which hide obfuscate the "To:" field.

In these scenarios, it'd be better to include the alias in the email body so users can act accordingly.