For scale and redundancy reasons we operate each service from its own hostname. So we always recommend using the most relevant hostname for incoming and outgoing servers in mail clients. These are as follows:
However, for compatibility reasons and to help ease migrations, we automatically setup mail.domain for each of your packages.
Any clients already using these hostnames can continue to do so when the account is moved to Pixallus, and any new accounts added at Pixallus will have the same functionality.