HTTPMail
HTTPMail is a mail access protocol that allows you to access your mail from the server and leaves the email on the server.  HTTPMail provides similar functionality to IMAP, where by an Outlook Express or Outlook client can access and manage messages and folders on the server. Unlike IMAP, it does not require SMTP to send messages.

Another advantage that HTTPMail has over using POP and SMTP is that it can be configured to operate over Port 80, meaning that you can access your mail through corporate firewalls.

IMAP4
IMAP4 is a mail protocol that allows users to be disconnected from the main messaging system and still be able to process mail. Users can store messages on a local machine or on a server.

IMAP has distinct advantages over POP because it allows you manage multiple folders on the server. Mail can be accessed from different machines, as the mail is hosted on the server (unlike POP which deletes mail from the server after being accessed) and allows the user to just download message headers and envelope information, until the user selects the email to download. This is useful when operating over slow speed dial-up connections.

IMAP4 can break up and download specific parts of a multi-part email message (MIME). This means that instead of having to wait for an email with attachments to download, you can select only the text portion to download, and leave the attachments on the server.

IMAP4 allows you to have server hosted folders and subfolders.

IMAP4 Public Folders
Public folders are visible to all IMAP users in a specific postoffice, thereby allowing information to be stored centrally and made available to everyone on the system. This might include documentation on policy and procedures or internal memos.

POP3
Post Office Protocol. This is a mail protocol that enables emails to be retrieved from a remote mailbox. That is, it allows you to collect emails from an hosted account that you have hosted on a server to your own email software, such as Outlook, Eudora etc.

POP Retrieval
The POP Retrieval Service will download mail via POP from a remote POP server and deliver to a local mailbox. Users are able to configure their own settings from web mail.

This means you can retrieve your emails from different mail accounts and view it on their local mailbox without having to log in to each separate account.

SMTP
Simple Mail Transfer Protocol. SMTP is a protocol for transferring outgoing email messages from one server to another and also to accept email messages from other mail servers and email clients. SMTP is used with both POP3 and IMAP4.

Web mail
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