There are two ways to send automated emails to your suspects, prospects and customers. So called transactional emails and marketing emails.
The first type (transactional) is used to send people emails to interact with your service. Examples are a password reset or a sign up confirmation from your app.
The second type (marketing) are opt-in emails, used to keep your customers or subscribers informed about new developments, education and offers.
These two types of email automation are often implemented wrong, or not in tandem. Some teams use marketing email solutions to send out transactional emails, or worse, they use transactional email systems to send out marketing emails. This is a very easy path for your emails to land in junk folders (and to hurt the reputation of your email domain name).
Most email providers provide both transactional and marketing email services. Hubspot has an option to add transactional email to their service. MailChimp does marketing emails, and the transactional email equivalent is Mandrill.
Make sure your team is using the right technology for the rigth purpose. Also make sure your engineering team is not implementing their own SMTP sender function in your product. That's a real nightmare scenario.
To wrap up, here are just some examples of both categories:
Transactional email senders:
- Amazon SES (Simple Email Service)
- Elastic Email
Marketing email services:
- Constant Contact
- Campaign Monitor
Also, it might be worth at some point to pay for a dedicated IP address. Make sure to have the above implemented correct before you do, as it will impact the building of your own "IP"s reputation.