If your project has user registration, you need to have a way for users to reset their passwords (they get crabby if you don't).
I've always used Mailchimp for email campaigns. They have an integration with Mandrill for sending transactional emails – the type you'd need for resetting a password. However, you need to pay around $70/mo just to access Mandrill.
To save some money, I recently implemented Mailjet for transactional emails. Since I'm only sending a handful of these emails per month, the product is completely free. I haven't tried it, but apparently you can also use Mailgun for this too.
Hopefully this saves someone some money 💰
Another great alternative for transactional email is https://postmarkapp.com/. They have a free tier for 100 emails a month and the next one is 10k emails for $10. Using it on all my projects.
Nice tip! Their website doesn't mention the free tier