A mail server handles email with sendmail and POP programs. Sendmail processes outgoing mail and returns it if the address does not exist or if there is a glitch. POP collects incoming mail and creates a text file, which can get large. IMAP collects mail for web-based services. Mail servers are available on websites and ISPs, and spam filters can be installed. Running a local mail server provides privacy but is often prohibited due to spam.
A mail server is a Web server set up to handle e-mail with two programs installed: a sendmail program and a POP program. POP (Post Office Protocol) collects mail sent to you. Mail servers can be installed on the main web server or on a separate server.
The sendmail service allows the mail server to process outgoing mail. If an email address does not exist, the server will return the mail to the sender. If the server has a glitch while trying to deliver mail and fails, the mail may also be returned. In all cases where mail is returned, it arrives with an explanation or an error code. By reading the error code, you can determine why the mail did not arrive at its destination.
The POP program collects incoming mail. When receiving mail, it creates a single text file of accumulated messages for each email address. This text file can get very large. If the end user has configured their email client to delete mail from the server upon collection, the mail server text file is deleted when the mail is collected. Some people, however, store their email on the server. This is not only a privacy concern, but can also lead to malfunctions when text files get too long.
Another collector program is called Internet Message Access Protocol (IMAP). IMAP runs web-based mail services like Yahoo!, Hotmail, and others. If you use a website to collect mail, you are accessing an IMAP mail server.
Virtually every website domain is bundled with mail server functionality. Internet Service Providers (ISPs) also offer email services and mail server functions. If the server doesn’t offer built-in content filtering, you can install your own spam filter. Free spam filters are very popular and are available online.
A mail server program can also be installed locally on your computer. If you’re running such a server, mail doesn’t have to travel through your ISP, providing a degree of privacy. Running your own server also ensures that you’ll always be able to send or receive mail, even if your ISP’s mail server is down.
Unfortunately, many people who run their own mail servers use them to send spam. As a result, ISPs commonly prohibit it in their Terms of Service. However, some ISPs allow users to run their own server if they sign a contract that guarantees it won’t be used for spam.
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