Risks to e-mail

There are several inherent risks in the way e-mail functions. When you send e-mail to a recipient, it travels to an SMTP (Simple Mail Transfer Protocol) server either directly (if you’re using an e-mail client such as Outlook) or via a Web server (if you’re using Web-based mail, such as Hotmail). The recipient will receive your e-mail directly from the SMTP server or via a Web server.
During this journey, any unauthorized person can access your messages by exploiting vulnerabilities on the SMTP or Web servers. Your messages can be read and copied by anyone who has access to the computers and networks through which your messages travel. In fact, authorized system administrators on the SMTP servers can also read, copy, save, delete, and modify your messages before sending them on.
During this ‘eavesdropping’, it may be possible to gain access to your usernames and passwords. The mischief-monger can then wreak havoc by sending messages on your behalf. You may also receive messages from known e-mail IDs that have been created and sent by unauthorized users; such messages usually contain viruses, Trojans or ask you to reply to the message with sensitive personal information, such as bank-account or credit-card details.
What’s more, mail backups on SMTP servers store the e-mail in plain text; sometimes, messages that you sent or received years ago are easily available on these backups, long after you have deleted them.
The issues with e-mail are, therefore, manifold - the sender’s e-mail ID may be stolen and misused, without the recipient knowing about it; messages may be intercepted; or messages may be stored such that their content is easily accessible.
Encryption, digital signatures, and digital certificates are some ways of securing e-mail from these threats.

Ref:India syndicate