Email VS. Gmail
when sending emails to Gmail accounts.
https://litmus.com/gmail-tabs
You just send an email to the address they provide, and you'll be able to see where Google is sending your email. I'm sure that there are a number of other tools similar, some which may require an account to be setup before hand (Mail Mike is another). But anyway...
Just something to play around with. If for whatever reason your email is highlighted under a different tab, then play around with the headline and try again. There could be a huge difference in reach if you're not testing Gmail accounts. So just be sure to give it a go before you send out your next email.
Enjoy
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