IPWorks is a comprehensive framework of easy-to-use components for Internet development, including FTP, HTTP, SMTP, POP, IMAP, LDAP, DNS, SMS, SOAP, etc.
Apache Commons Net library implements the client side of many basic Internet protocols such as FTP/FTPS, FTP over HTTP (experimental), NNTP, SMTP(S), POP3(S), IMAP(S), Telnet, TFTP, Finger, Whois, rexec/rcmd/rlogin, Time (rdate) and Daytime, Echo, Discard and NTP/SNTP