Can I use theCloud/vGRID's SMTP server to relay email from my VM?

The general answer is no, as we don't permit anonymous access to our SMTP servers due to misuse in the past which has caused issues with our customers using our Hosted Exchange environment.

In saying that, if you do have a hosted exchange account on vGRID you can use those details to authenticate with, otherwise you can look at creating another mail account for your requirements to send from.

Other options that can be looked into include installing the SMTP feature on Windows Server and running your own simple SMTP server, or relaying via another mail provider you may have an account with.