Developers Documentation



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User Tools

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IMAP and POP Server

ClearOS provides both POP and IMAP servers for providing mail delivery to desktop clients.


If you did not select this module to be included during the installation process, you must first install the module.

You can find this feature in the menu system at the following location:

Server|Mail|POP/IMAP Server


The base mail domain is used by a number of apps: SMTP Server, IMAP, Mail Filter, etc. Each app saves this information in its own configuration file, but we really only want to see the domain in one place in the user interface. That's where the Mail Settings app comes in.

  • Go to System|Account Manager|Account Manager to make sure the accounts system (users/groups) is running.
  • Go to System|Settings|Mail Settings to set the mail domain.
  • Go to System|Accounts|Users to create a few users. Please make sure the SMTP Server User and IMAP and POP Server User are enabled for the user.
  • Go to System|Accounts|Groups to create a group or two. You will see a new option when adding/editing a group: Distribution List. If you leave this option enabled, the group becomes a mail distribution list (e.g. will go to all the members of the sales group).
  • Go to Server|Mail|IMAP and POP Server and start all the servers (if not running).


Server Configuration

Mail Server Protocols

The mail server supports four different protocols:

  • IMAP
  • Secure IMAP
  • POP
  • Secure POP

We strongly suggest using the secure protocols if possible. Keep in mind, you will need to generate an SSL Certificate to enable the secure protocol.

Push E-mail

Some mail clients support the push e-mail feature (also known as the IMAP Idle feature). With this feature enabled on both the server and client, e-mail will appear in your mailbox as soon as it arrives. This feature is most useful on wireless and handheld devices. The following mail clients are known to support push e-mail (IMAP Idle):

Mail Client Configuration

Secure POP - Mozilla Thunderbird

If you are using Mozilla's Thunderbird, click on Tools|Account Settings, then select “Server Settings” from the navigation bar. Ensure the Use secure connection (SSL) checkbox is enabled.

Secure POP - MS Outlook/Outlook Express

For Outlook and Outlook Express, click on Tools|Accounts, select the account you wish to configure and click on the button.

Next, click on the “Advanced” tab, and ensure the “This server requires a secure connection (SSL)” checkbox is enabled.

Secure POP - Other Mail Clients

For other mail clients, similar set-up/configuration will exist. Please refer to documentation for your mail client for specific instructions.


Do not forget to open up firewall ports for e-mail. You only need to open the POP or IMAP ports if you plan on picking up your mail from outside your local network. The default ports are listed below:

  • POP - 110
  • Secure POP - 995
  • IMAP - 143
  • Secure IMAP - 993

content/en_us/6_imap_and_pop_server.txt · Last modified: 2015/08/07 00:01 (external edit)