IMAP and POP Server
ClearOS provides both POP and IMAP servers (cyrus-imapd) 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:
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 Managerto make sure the accounts system (users/groups) is running.
- Go to
System|Settings|Mail Settingsto set the mail domain.
- Go to
System|Accounts|Usersto 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|Groupsto 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. firstname.lastname@example.org will go to all the members of the sales group).
- Go to
Server|Messaging|IMAP and POP Serverand start all the servers (if not running).
Mail Server Protocols
The mail server supports four different protocols:
- Secure IMAP
- Secure POP
We strongly suggest using the secure protocols if possible. The IMAP and POP server will use its own self-signed certificate out of the box. We recommend that you obtain a commercial certificate in conjunction with the Certificate Manager or a free Let's Encrypt Certificate to secure the protocol. Instructions on using the Let's Encrypt certificate are in this HowTo.
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):
- Thunderbird - Many platforms
- Chattermail - Palm Treo
- FlexMail - Windows Mobile
- K-9 Mail - Android
Mail Client Configuration
Secure POP - Mozilla Thunderbird
If you are using Mozilla's Thunderbird, click on
Secure POP - MS Outlook/Outlook Express
For Outlook and Outlook Express, click on
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.
If you open any incoming POP or IMAP port to the internet, then you are more exposed to user/password hacking so strong passwords are highly recommended. By way of mitigation, it is recommended to install the Attack Detector app and enable it for cyrus-imap. The IPS Updates enabled for IMAP and/or POP are also recommended.
- POP - 110
- Secure POP - 995
- IMAP - 143
- Secure IMAP - 993
Only open the ones you require.