I use it for outgoing SMTP from my gmail agent, identified as coming from [email protected] ... I added this step because gmail doesn't do DKIM and DMARC, so my emails were being marked as spam by aggressive systems. mail-tester.com rates me at 9.3/10, and the missing points are mostly because my domain is less than 4 weeks old.
Gmail will drop support for sending from custom domains (at least those that aren’t hosted with them) next year btw. That’s why I’m looking for another smtp solution.
In the mean time I’ve checked them (smtp2go) a bit and apparently they do work on having a good reputation and allow you to add them as a smart host to your own smtp server so looks like I’ll give them a try.