[ryanb]

Yep, this is called a "manual action" by Google, and they'll often tell you exactly what you're doing that they find offensive. Usually this involves buying spammy backlinks. You can resolve the issue and ask them to re-evaluate your site by submitting a Reconsideration request.

https://support.google.com/webmasters/answer/9044175?hl=en

[ngold]

Good stuff. Tell us more googly stories of interest. This is super fascinating.

[ryanb]

Engagement on links clicked in Gmail is likely a ranking factor in Google search.

We've done studies with popular e-mail newsletters that showed URLs performing better in search on days when they've been sent out to hundreds of thousands of people.