[remus]

I stopped using them because of their awful support. The shared IP address our emails were coming from must have gotten on to a blacklist because 35% of our emails started being rejected overnight (not even making it to spam!) and their response was "just wait a few weeks, email reputation improves with time" like you can run a business when there's a 1 in 3 chance of any communication with a customer disappearing?!

Moved to SES and been smooth sailing since (and a lot cheaper).

[petercooper]

The support has gotten worse since Twilio took over. Even if you ignore delays, they struggle to understand problems quickly. We've had a couple of incidents where they are hitting our webhook over and over for days and prove unable to diagnose it properly.

The service at a technical level is pretty good. It does the job, the pricing is fine, and deliverability is good. I think their IP address space is considered a bad neighborhood by some spam filtering systems though, since we can't send email to systems protected by Mimecast (sorry Red Hat, Packt, Siemens, et al.) despite our own dedicated IPs having very solid reputation and histories.