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Explain POP3/IMAP & Mail FAQs


There are two main ways that users can access their email. POP3 (Post Office Protocol 3) is the standard way which has been around for decades. It is very similar regular mail. Messages are delivered to your computer, put in your mailbox, and are then your responsibility.

The other, newer, method is IMAP (Interactive Mail Access Protocol). As you might guess by the name, it is not like the mailbox on your house. With IMAP mail is delivered to the server, and you connect to the server to see your mail. The mail is not stored on your machine. When a message is marked as read, it is marked as read on the server, not on your computer.

At first this may seem kind of backwards, but what IMAP lets you do is access your mail from different programs, different computers, or even via a web page and your mail will always reflect all your changes.

Advantages of POP3
  • Email is available when you are offline
  • Email is not stored on the server, so your disk usage on the server is less
  • Just about any email client (software) supports POP3
Advantages of IMAP
  • Email is available from any machine you happen to use
  • Email is stored on the server, so your email cannot be deleted/destroyed if your computer should happen to crash, be stolen, or destroyed
  • You can access IMAP mail via the web, without even needing a mail client installed. This means you can check your mail from someone else's machine or even a public terminal and not have to worry about the security of your passwords.
  • Some IMAP clients can set up rules for "server side" filtering. This means that you could put all the emails from current customers into one mailbox, and filter other mail (potential new customers) to another mailbox. This can be done automatically by the server instead of setting up manual filters in whatever software you happen to have. This also means that in most IMAP clients you can subscribe to only certain mailboxes. For example, at work you could subscribe to only client mail, at home only to personal mail, and on your laptop to all your mail. All with a single account.
  • If you read a message on one computer, it is read on any other computer you use to access your mail. If you reply to an email on one computer, that reply is available on any computer you use.
Disadvantages of POP3
  • Can be much slower to check mail
  • Much harder to do server-side filtering
  • Mail is inaccessible from other machines
Disadvantages of IMAP
  • Mail is not usually available if you are offline.

FAQs (Frequently Asked Questions)

Q. What do you do about spam?

Spam, or unsolicited commercial email (UCE) is a huge problem. In 2001 it represented over 50% of email traffic; latest estimates for 2005 indicate it will be well over 90% of all traffic. Because of this abuse, we are extremely proactive. ALL mail is checked for spam and suspected spam is tagged with a (Spam? #) in the Subject where # is anything from 5.0 to 100+. Anything with a score of 6 or higher is almost certainly spam, and anything with a score of 9 or higher has a less than 1/10,000th chance of not being spam. These tags make it easy for you to sort/filter your mail.

Q. Will you delete my spam for me before I download it?

No. Since spam filtering is not 100% effective we will never delete suspicious mail. You are free to setup filters on your own. Spam will be automatically deleted from the spam folder after 7 days, giving you plenty of time to recover it.

Q. Will you delete ANY email?

No. Once we've received mail for you we will deliver it. However, we BOUNCE (reject) any email with a virus-like attachment (.exe, .pif, .scr, etc). If someone sends you an .exe file they will get a bounce email telling them we don't accept executable attachments. They can zip the file and resend it. NB: This does not mean that .zip files are safe to open. In fact, some recent viruses specifically use the zip format. Never open an unknown or unexpected attachment. If you're unsure, email the person asking if they really sent you the file.

Q. All the mail from this user is getting marked as spam, but it's not. How do I change this?

You can create a folder on your IMAP server named "sa-learn-ham" and copy any mail that you don't want marked as spam to that mail box. This MIGHT help. The spam filters will check that mailbox and try to use any messages in it to learn what is and is not spam. You might also forward a sample message to abuse@covisp.net and we will see if there's anything we can recommend.

Q. Someone tried to send me a 50 Megabyte photo and it keeps bouncing. What's the problem?

The email system is not intended for files that large. Files that large should be place on a public website, ftp, copied over SSH, or transferred in some other manner. Our email server will reject any message over 10MB in size.

Q. Why doesn't the outgoing mail server require authentication?

The mail server keeps track of everyone who connects to check their mail. When someone sends mail, it checks to see if they are "known" to the server, if they are, it allows the mail to be sent, if they are not, it doesn't. This method is quite secure.

Q. Why isn't the login password encrypted?

The login password for self-managed IMAP accounts is only sent over a secure connection (SSL or Secure Socket Layer). Since the connection itself is secure, there is no reason to encrypt the password.

Q. Can I use a secure IMAP connection with my email account?

Only if you are using the self-managed web interface to manage your email. If you would like your email accounts converted, just email us.

Q. Can I use the unsecured IMAP connection with my email account?