A lot of mail merges are starting to get caught by spam filters. It would be great if YAMM automatically spaced emails out by 5 to 20 seconds (at random). It would take longer to get through the 100 emails, but at least more would end up in recipient's inboxes.
While you're at it, you could have YAMM automatically pause when it hit the 100 limit until 24 hours had passed, and then automatically continue down the list.
Please ask your IT department to properly set up the SPF records for your domain, otherwise there’s a high chance to get caught by spam filters.
eg on domain carbonlighthouse.com, there are some issues:
Please follow this documentation from Google to set up everything properly: