I am building a Rails application with the following functionality: when receiving emails from users, parse the content, perform some tasks and send update emails to users, with low latency.
For receiving emails, I have MailMan gem. For sending email, I have ActionMailer. For mail server, I am using Gmail with Pop3.
It seems that SendGrid is a popular thing for email. I have a hard time understanding what exactly SendGrid does beyond ActionMailer. Is SendGrid an SMTP email server and an alternative to my Gmail Pop3? Does it handle incoming emails?
What are the advantages over ActionMailer?