1. M.T. Banday, J.A. Qadri, N.A. Shah, A practical study of E-mail communication through SMTP. Working Papers on Information Systems, Sprouts. ISSN: 1535-6078, 10(20) (2010)
2. Klensin, Simple Mail Transfer Protocol, IETF RFC 2821 (2001)
3. J. Klensin, N. Freed, M. Rose, E. Stefferud, D. Crocker, SMTP service extensions (1995). 1017487RFC1869
4. P. Tzerefos, C. Smythe, I. Stergiou, S. Cvetkovic, A comparative study of simple mail transfer protocol (SMTP), post office protocol (POP) and X.400 electronic mail protocols, in Proceedings of the 22nd Annual IEEE Conference on Local Computer Networks (1997), pp. 545–554
5. M. Crispin, RFC 3501: Internet Message Access Protocol Version 4rev1. IETF (2003)