Hmmmm...

My suggestion would be, just email them and say:

Thanks for choosing us,

Welcome to XXX server we're glad that you've chosen us to be your provider. We will try to help you and reply to your TTs as soon and as fast as possible but do bare with us as sometimes we get swarmed.

Also include where to send what email. Eg. Please send your support emails to support@xxxx.com. Billing email to billing@xxx.com and etc...

Lastly... THANK THEM for choosing you guyz (again).

Hope this helps!