Check out Mailgun: http://www.mailgun.com/ . It's a service rather than a library, but it handles incoming emails and has wrapper libraries in a number of languages.
We use Mailgun (Mailgun Routes) at our startup to handle email sent into the application. It works fantastic - it POSTs the email neatly structured into To, From, CC, Subject, Body etc fields and also extracts the text of the email from the Body without the signature and the quoted text which is invaluable (and isn't done by other services such as Sendgrid, Postmark, AWS etc).