Every EJB server which is compliant with the EJB 2.0 spec must support JavaMail 1.1 Standard Extension (for sending mail only). Some servers also support the JavaMail API that allows connection to a message store, which could be an IMAP server or POP3 server, that contains the folders and messages which the server can access and read.
Should you use EJB for e-mail? I'd expect e-mail to be part of some business process which is running in an EJB container, as it would normally make no sense to use EJB just for e-mail.
SCJP 1.4, SCWCD 1.3, SCBCD 1.3
Don't get me started about those stupid light bulbs.