SMTP is another highly developed and widely used Internet protocol. SMTP is even more mature than HTTP and widely and robustly delivers email messages in very high volume everywhere in the Internet. SMTP has the distinct advantage for asynchronous response delivery, since the messaging paradigm of email is naturally one-way.
Disadvantages of SMTP include the poor support for development of non-email applications and the sometimes quirky treatment of mail that is misdirected. SMTP is also subject to abuse in the form of high volume unsolicited message traffic (SPAM) and mechanisms for the transfer of viruses and worms. There is little that can be done about SPAM within the context of location-based services. Dealing with malicious content is quite feasible. The transport unpacking function has no need to allow or enable any mechanism for execution of any part of the service request messages or other information in the SOAP envelope. In some cases it may be useful to scan these elements for viruses and that is certainly true if there is any possibility of using the underlying mail system as a relay point.