Be aware gmail has limits I think its 500 daily quota and I don't remember how many emails can be sent per second, but you can send 50 at a time and wait a minute or 30 seconds and send the next batch, if you're sending personalized emails IE dear MYI its better to use single email per invitation not to be marked as spam, otherwise use bcc and send to 50 at a time, if any of those emails aren't active you'll get a bounce back for that specific email the rest will continue sending, if you're using bcc put something in the to: and that email will be seen by all recipients