Thanks for that info. I am currently using brevo.com and the dashboard says that over 98% of mails were delivered. I already started to register Amazon SES, currently waiting for the DKIM verification. So seems like a good time to switch soon. I hope that helps, since smtp servers and email domain warmup is not really a topic I know much about honestly.

Update: Will add SSO soon

I've firstly searched for subreddits that are international but none of those allowed me even to just pitch the idea. Then I suddenly found German subreddits for searching friends and they had either no rules, no active mods, or the mods just allowed me to post. I searched a few city subreddits of Germany as well. And yea, I am actually from Germany so it made it even more easy then.

The matching works on 5 dimensions, such as - social energy, directness, worldviews. Each weighted on how important it is for you. The matching also tries to pair people with the same activity on the app, means someone who just turns in once a week won't be preferred in matching with someone who opens the app daily. There are also some hard and soft criteria's users can configure in their matching settings, such as age range, locations, gender, etc.

I hope that answers your questions. I have a deep dive on the matching system on my faq page if you're curious