this was a response I got
Well, six seconds is around the high end of the usual threshold for PHP mail or mail sent via SMTP that is being sent out as a result of a contact form or script on the (gs) Grid-Service. As I previously mentioned, the Grid is a clustered type of server where resources from each server in the cluster are shared among customers. When PHP mail it sent out it is sent from any number of web nodes and not necessarily only from your (gs) Grid-Service itself, depending on load. If you need instantaneous sending capability it is recommended that you either further optimize your script, use a dedicated mailing service provider (such as MailChimp), or consider hosting on a VPS server where resources are not shared.