When comparing Mandrill vs Sarv Transactional Email Service (Sarv TES ), the Slant community recommends Mandrill for most people. In the question“What are the best transactional email services?” Mandrill is ranked 3rd while Sarv Transactional Email Service (Sarv TES ) is ranked 10th. The most important reason people chose Mandrill is:
Simply set your SMTP server to `smtp://user:API_KEY@smtp.mandrillapp.com:465` and you're good to go. There are libraries for using the API in a variety of languages, including Node.js.
Specs
Ranked in these QuestionsQuestion Ranking
Pros

Pro Both SMTP and HTTP APIs are easy to setup
Simply set your SMTP server to smtp://user:API_KEY@smtp.mandrillapp.com:465
and you're good to go. There are libraries for using the API in a variety of languages, including Node.js.

Pro Clean UI
The UI is very clean and good-looking overall. While the Analytics may seem basic and not very detailed, the dashboard interface is very clean which also helps with the set up.
The left side of the page has the navigation to different parts of the dashboard. The main view displays all the most important data and analytics that you may need (emails sent, deliverability, reputation etc...). While the navigation itself is pretty straightforward and self-explanatory.
Pro Has sandbox mode for testing
Instead of sending real e-mails out, can use test keys which allows to test without actually sending out real e-mails. These test keys can also safely be shared inside the team since they cannot be used to send real e-mails on your behalf.

Pro Clear API documentation
The API documentation is very clear and makes it pretty easy to set up you application with Mandrill's API quickly and painlessly.
Pro Great mobile apps
Mandrill has companion apps for iOS and Android that allow monitoring the service using a smartphone.
Pro Highly customizable templates
Mandrill has made templates a core part of the product as they simplify the payload when compared to sending the full HTML each time and allow non-developers to design the template.
Mandrill uses the flexible content formatting of MailChimp templates. This paired with the API access to template management, gives the user a great deal of flexibility.
Pro Webhook Reporting
Mandrill provides and Event API also or "webhooks" through which it registers events when they occur. So when an activity occurs, the application server is called along with the activity that occurred. Events include opens, clicks, bounces, deliveries and spam complaints.
Pro User friendly rules engine
Mandrill allows setting up rules in a non-technical way.
Pro Great MailChimp integration
Mandrill is made by the same company that made MailChimp. As such, both products work very well with each other.

Pro Outgoing messages log
You can see the contents of all messages that Mandrill has sent out, for free for the last 24 hours, or for some cents per thousand messages if you need a longer retention period.
Pro Pay as you go service
Sarv offers two plans; cost per subscribers, and cost per email.
The cost per subscriber plan is 25,000 subscribers for INR 6,050 monthly. The next plan, cost per email, gives a user 25,000 emails for INR 1,000 monthly.
Pro 24/7 friendly customer support
24/7 support via a support ticket system, a toll-free number, e-mail, and live-chat.
Pro High and instant email delivery
Sarv allows you to analyze your open and click reports according to the geolocation of the subscriber and target your customers directly based on their whereabouts.
Pro Free trial offered, with no credit card needed
Sarv offers a 30 day free trial, and doesn’t require a credit card. The free plan includes 1000 emails. You just need to enter your email id and must verify your account. You’ll get a user id and password.
Pro A user-friendly interface
Drag and drop editor that makes it easier to design creative mailers. No need to have skillful hands in HTML and other heavy software, just to design a template.
Cons
Con Has a bad history
When they decided not to support a free tier anymore they've set up a withdrawal period of only 2 months for existing customer before it stopped working (even for people who bought credits to send more than that free tier). Meaning people using it had a month to switch to another solution or start paying $20/month or more.

Con No free plan
There used to be a free plan which offered 12,000 free emails per month. Unfortunately it has now been discounted and there's no other free plan anymore. If you want to use Mandrill, you have to pay $20/month or more.

Con The documentation is split between two sites
The API is documented at https://mandrillapp.com/docs/, while howtos are in the Knowledge Base. Searching on the former for "Handlebars" doesn't find anything useful about using Handlebars.

Con Template rendering doesn't support Handlebars
The templates.render
call doesn't support Handlebars. This makes complex integrations more difficult. You can, however, use handlebars with messages.send
and messages.sendTemplate
.
Con Not support adult and dating emails
Con No web forms
