I read MailChimp is to send bulk emails and Mandrill for transactional emails.
I am not so familiar with these terms. Can I have bulk transactional emails when I have a lot of users? or does bulk emails apply just when I sent one copy to many users?
My app is sending emails a few because is new, but it could grow. Will I be sending bulk emails when application grows? event if these emails are transactional?
What is a transactional email?
Transactional emails are typically non-marketing emails. Usually they are a thank you, confirmation, invoice, receipt etc. Something that is related to a transaction your customer made. General newsletters or promotional/sales emails (anything sent in bulk to a list) is not transactional.
Here is Mailchimp's What is transactional email link