Mailchimp Transactional Email

Pros

Mandrill provides a simple and well documented API and has libraries and integrations available for many major web frameworks and languages. Making use of it for simple email sends is a fast and easy process, and it provides additional functionality for black lists, white lists, bulk sends, static IPs, etc. Their dashboard makes it extremely simple to see all the emails sent to a given address along with full content and reasons why sends failed or were delayed, which is a great for debugging and testing. They also provide analytics and send, receive, open, click, and bounce rates.

Cons

The service used to be much cheaper, but costs went up sharply when it was reabsorbed back into Mailchimp. Still an excellent service, but harder to recommend without reservation.

Pros

Mandrill (now interated inside Mailchimp) has been a solid and reliable transactional email provider, with great delivery rates, very slow spam scores and ultra-fast reception speed. It provides useful and flexible reports and great dashboards too.

Cons

In order to keep it's spam reputation high it takes some effort to set up a new email domain in Mandrill. You have to prove you own the DNS and configure a SPF/DKIM record.

Pros

Transactional Emails is really necessary in today's world, we get a much better open rate and much better interaction when we use this system rather than a simple mass email message. Totally recommend this set up, and it has the the facilities to set up everything pretty easily.

The API documentation is robust, and their service uptime is great, it does what is advertised.

Cons

The fact that I need to have a mailchimp paid account and to get into Mandrill through Mailchimp is a little weird, but it's minor in the grand scheme of things. I don't use Mailchimp, our marketing department uses an alternative, but our developers use Mandrill.

Pros

I run a busy social network. Around 6,000 users total, and 300-400 online at any given time. Due to this, I needed a transactional email service that had great deliver-ability for invitations, verifications, password changes, etc. Mandrill was recommended to me, and we were completely happy with the service. Unfortunately, when they bundled Mandrill into Mailchimp, we couldn't afford it anymore.

Cons

Unfortunately, bundling services did no favors. What previously was affordable for us no longer was. While the service is great, the way the change was implemented was sudden, leaving companies little time or recourse to find other options quickly. That solidified my decision to leave- most companies would grandfather in existing members, offer a lower rate, something. They simply provided us with addresses for other services, losing customers in the process.

Pros

Very fast delivery with exceptional delivery rates;
Does a great job keeping reputation high;
Very nice dashboards and reporting;
Ability to segregate into sub-accounts;
Very easy to integrate with MTA's and API clients;
Great documentation;

Cons

Domain validation could be made simpler;
Roles and permissions should be more flexible;
Once Mandrill got integrated with Mailchimp the pricing model became less attractive;