[dchesterton]

We're doing the same. I re-wrote our code over the weekend from sending solely through Mandrill, to splitting our traffic 50/50 between SendGrid and SparkPost. I'm going to implement a similar strategy for some other external services we rely on and I've open sourced the Go code [1].

This also has the benefit that if one service goes down, we can automatically fallback to the other with (hopefully) no downtime. Most email providers have a limit to what you can send until you're established with them, so using another provider as a standard backup isn't feasible, as suddenly sending 1,000's of emails a day will see the account get suspended pretty quickly.

Plus, if one of them goes out of business or changes their terms with little notice, like Mandrill, we should have a bit more time to work around it as at least one service will work.

[1]: https://github.com/dchesterton/go-service