There are various kinds of email providers. There are paid and free ones, possibly sustained by advertising. Some allow anonymous users, whereby a single user can get multiple, apparently unrelated accounts. Some require full identification credentials; for example, a company may provide email accounts to full-time staff only. Often, companies, universities, organizations, groups, and individuals that manage their mail servers themselves adopt naming conventions that make it straightforward to identify who is the owner of a given email address. Besides control of the local names, insourcing may provide for data confidentiality, network traffic optimization, and fun.
Mailbox providers typically accomplish their task by implementing Simple Mail Transfer Protocol (SMTP) and possibly providing access to messages through Internet Message Access Protocol (IMAP), the Post Office Protocol, Webmail, or a proprietary protocol. Parts of the task can still be outsourced, for example virus and spam filtering of incoming mail, or authentication of outgoing mail.
Many mailbox providers are also access providers. Not the core product, their email services could lack some interesting features, such as IMAP, Transport Layer Security, or SMTP Authentication —in fact, an ISP can do without the latter, as it can recognize its clients by the IP addresses it assigns them.
AOL Mail, Hotmail, Lycos, Mail.com, Yahoo! Mail, launched in the 1990s, are among the early providers of free email accounts, joined by GMail in 2004. They attract users because they are free and can advertise their service on every message. According to Jurvetson, Hotmail grew from zero to 12 million users in 18 months. That was before it was bought by Microsoft.