SMTP

• http://stackoverflow.com/questions/15796530/what-is-the-difference-between-ports-465-and-587
• http://stackoverflow.com/questions/3484947/why-should-i-convince-developers-to-use-port-587-for-all-smtp-communication

Vs IMAP vs POP3:

• IMAP: download email on a remote server from another one
• POP3: download emails locally from remote server