Glad to hear you like Sidebar!

And you're right, the open rate is much lower than usual (19% vs 63% for the one before). I didn't noticed it before because the daily edition containing the same referral link that I sent on the same day went through fine.

This happens from time to time and I'm not sure what I can do about it.

I honestly don't understand how Gmail's spam filter can be so "dumb" (at least from a human point of view). You'd think that if someone open, reads, and clicks emails from a particular address regularly, the filter would be smart enough to know that there's a very high probability it's not spam.