I was looking over some of my past Mandrill reports today and I realized I had a rather large dataset so I thought I'd share it for some insight into why, in my opinion, Mandrill is the best transactional email service on the market.
Honestly it doesn't look THAT fancy when it's displayed like this, but the numbers speak for themselves.
Out of 6,354,229 emails sent, 6,353,207 were delivered.
Which is pretty much a 100% deliverability rate.
My billing recharge rate was set to $10, and I received a total of 111 recharges for this specific dataset. Mandrill's recharge rate isn't always accurate and sometimes it goes over, but it's a marginal amount.
Another great feature about Mandrill is their webhooks, which I set up to deal with hard bounces, unsubscriptions, and spam complaints. This way you can stop sending emails to people who don't want them as quickly as possible.
Here's the quick PHP by the way to accept an incoming webhook for a problem email: GitHub
Mandrill also supports SSL and TLS for security/encryption at the SMTP level, which means that it can be utilized for more than just general transactional emails.
In conclusion: I am in love with Mandrill, and the bottom line is: their deliverability rate cannot be beat.