emlx Used by Apple Mail.
msg Used by Microsoft Office Outlook and OfficeLogic Groupware.
mbx Used by Opera Mail, KMail, and Apple Mail based on the mbox format.
Some applications (like Apple Mail) leave attachments encoded in messages for searching while also saving separate copies of the attachments. Others separate attachments from messages and save them in a specific directory.
URI scheme mailto
Main article: mailto The URI scheme, as registered with the IANA, defines the mailto: scheme for SMTP email addresses. Though its use is not strictly defined, URLs of this form are intended to be used to open the new message window of the user's mail client when the URL is activated, with the address as defined by the URL in the To: field.[68][69] Many clients also support query string parameters for the other email fields, such as its subject line or carbon copy recipients.[70]
Main article: Webmail Many email providers have a web-based email client. This allows users to log into the email account by using any compatible web browser to send and receive their email. Mail is typically not downloaded to the web client, so it cannot be read without a current Internet connection.
The Post Office Protocol 3 (POP3) is a mail access protocol used by a client application to read messages from the mail server. Received messages are often deleted from the server. POP supports simple download-and-delete requirements for access to remote mailboxes (termed maildrop in the POP RFC's).[71]POP3 allows you to download email messages on your local computer and read them even when you are offline.[72][73]
IMAP email servers
The Internet Message Access Protocol (IMAP) provides features to manage a mailbox from multiple devices. Small portable devices like smartphones are increasingly used to check email while traveling and to make brief replies, larger devices with better keyboard access being used to reply at greater length. IMAP shows the headers of messages, the sender and the subject and the device needs to request to download specific messages. Usually, the mail is left in folders in the mail server.
