Actionstep offers multiple ways to send and receive emails. Office 365, Gmail, mailgun (built-in), and SMTP mailboxes can be setup to send emails. Actionstep plugins, add-ins, mailgun (built-in), and POP3 collection can be used to get emails into Actionstep.
https://actionstep.zendesk.com/hc/en-us/articles/1500002228261-Email-in-Actionstep in Actionstep Help Center