A mail server is a computer that serves as your electronic mail box, or it could even be considered your electronic post office. These servers that are running on the same software, exchange emails across networks, and they would more or less run on the same email protocol, and email attachment as well graphics that they would use. Companies have their own ISP, otherwise known as your Internet Service Provider, and these ISP servers would have their own mail servers and deal with their own clients' emails.
How does sending and receiving an email work? When you send an email, and the recipient of that email belongs to the same network, the mail server, or the mail transfer agent, sends the email to the email address on the same network. Should you send out an email to another mail server, which means the email address does not belong to the same network, your email is then passed to your mail server first, which is then transferred to the mail server of your recipient. When you then send an email, your email program like Eudora or Microsoft Outlook, would send the email to the mail server. There are different systems to send out these mail servers, and an example of these would be SMPT, which means Simple Mail Transfer Protocol, or the ESMTP, or the extended SMTP. While receiving the emails, you also have to use a specific program for mail receiving which could be any of these systems, POP3, or the Post Office Protocol 3, or the IMAP, or the Internet Message Access Protocol.
Having explained how the email process works, what should work best for your system when you receive email messages that you do not need?
These are emails that you call 'spam messages'. They are harmful in terms of using up the storage area for your mail server. Spammers would take advantage of some mail servers if these mail servers are set up to have the 'catch all email account'.
In such cases, there are two options to choose from. You either choose to use the 'fail' option, or you can go 'blackhole.'
These options are, of course, only handled by your IT department. As an email user, you need to know what options should have better results.
The blackhole option accepts all types of emails, regardless if you do not know the email address sending you an email. After these emails are received in your mail server, they are then deleted. The disadvantage though is that it downloads the email received, taking up bandwidth, and space in your mail server, before it actually deletes the email.
The fail option, on the other hand, stops the email before entering the mail server. This is advantageous to your mail server and to the sender because a message will be sent back to him telling him the recipient did not receive his message, to which he could amend. The email address could've been incorrect, so the sender could re-send the message to the right email address.
Read The Whole Article - How Mail Server Works
