How to stop outreach template being marked as spam?

I'm about to start reaching out to web masters to promote my website. I have a standard outreach template that I'm going to hire a VA to use (email to webmasters).

However I know from experience if you send a message to Gmail and a few users mark it as spammy (even in error) then obviously Gmail applies a text match to all the rest you send and spam folders them.

I could try and vary the message text 50% each time but I don't trust a VA to do this.

How do you guys get around this?