I will add more details to these providers in the future, but here’s a list of the common WordPress/WooCommerce-compatible SMTP providers. I referr to these as dedicated SMTP providers because that’s the common description, but many are just general Email Service Providers (ESP’s).

Amazon SES is one of the most cost-effective ways to send large volumes of email (see their pricing page to figure out your particular scenario). The unofficial Delicious Brains plugin is probably the best way to integrate it.

Mailgun is free if you’re sending less than 625 emails per month (you may find older sources saying 10,000, but that was changed in January 2020). Their plugin is fairly well-reviewed.

Mailjet is free if you’re sending less than 6,000 emails per month. Their plugin is fairly well-reviewed.

Mandrill is Mailchimp’s “transactional” email service, and is priced by “block” of 25,000 emails. You have to buy a minimum of one block at $20. Their plugin is fairly well-reviewed.

SendGrid is free if you’re sending less than 100 emails per day. Their plugin is somewhat buggy, however, so I’d suggest using an independent SMTP plugin.

SendWP is a WordPress-specific provider with a $9 per month account. Their plugin doesn’t yet have any ratings/reviews, probably because it only works with their paid service.

SendInBlue is free if you’re sending less than 300 emails per day. Their plugin is fairly well-reviewed.

SparkPost has a free test/developer account limited to 500 emails per month. Their plugin has mixed reviews and hasn’t been updated in quite a while.