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How To Switch the Mail Server From Courier To Dovecot in WHM

Posted on by dpepper
Reading Time: 4 minutes

In cPanel/WHM versions up to 11.52, users were able to choose between two mail servers: Courier and Dovecot. Courier was selected by default, and most cPanel users never had reason to switch. However, beginning with cPanel/WHM version 54 (the preceding “11” was dropped), Courier has been deprecated. cPanel will no longer support Courier in future releases, and will automatically convert the mail server to Dovecot if it has not been done manually within 30 days of updating to cPanel/WHM version 54.

Pre-Flight Check

  • This article explains how to manually switch the default mail server from Courier to Dovecot on a cPanel server.
  • To change the mail server, you will need to be able to log into WHM as root.
  • If Dovecot is not manually selected as the default mail server, cPanel will automatically perform the conversion, but will continue to send email notices each day until the switch is made.

Will Switching from Courier to Dovecot Affect Email?

The short answer is “no”. cPanel’s selection of Dovecot as the new default is based on the fact that it requires less memory, provides better performance, and has a wider range of configuration options than Courier. Dovecot is significantly faster, in part because it indexes the directory where mail is stored, and is fully compatible with Courier’s format.

Switching the mail server from Courier to Dovecot will not affect:

  • email accounts
  • email client connection settings
  • mailboxes
  • mail folders
  • forwarders
  • spam rules
  • existing email messages

Aside from being faster, email will continue to work as it did before and the switch should be transparent for email users. There are, however, two items that you will want to note:

  • There is an option to Convert Mailbox Format when switching the mail server in WHM. To ensure a seamless transition for email users, that box does need to be checked. If the box is left unchecked, previously read messages could be mistakenly flagged as unread, and some email users may need to re-subscribe to IMAP folders in their email clients. That would not affect the data itself, but could create extra work for email users, and is easy to avoid by following the instructions below.
  • Some POP3 email users, depending on their email client configuration, could see messages that they previously downloaded from the server downloaded again by their mail clients when they connect for the first time following the switch. While an annoyance, it poses no risk to the messages themselves.

Step #1: Switch to Dovecot

    1. In WHM, click on Mailserver Selection in the left menu.Mailserver Selection in WHM
    2. Now, select the radio button next to Dovecot, check the box next to Convert Mailbox Format and then click the Save button at the bottom of the page to implement the switch.Select Mailserver in WHM
      • Note that the Convert Mailbox Format box must be checked to preserve information about read messages, mailbox subscriptions, etc. Doing so is necessary to ensure a seamless transition. If the box is not checked, data won’t be lost, but previously read messages could be flagged as unread and email users may need to re-subscribe to IMAP folders in their email clients.
      • As noted above, the transition should be completely transparent for IMAP email users, but there is a chance that some POP3 users (depending on mail client configuration) could see messages they downloaded from the server prior to the switch downloaded again.
      • The mail server switch should have no effect on a user’s emails themselves.

Step #2: Check Service Monitoring Settings

Once you have changed the mail server from Courier to Dovecot, you may wish to enable cPanel’s service monitoring for the new mail server. If you previously had enabled cPanel service monitoring for Courier, you can do so for Dovecot as well.

That can be done in WHM under the Service Manager menu item. You will want to check the entries for POP3 and IMAP Server. To enable cPanel service monitoring for Dovecot, simply ensure that the checkbox in the Monitor column is checked, and click the blue Save button at the bottom if it is not. If the box already was checked, there’s no need to re-save the settings.

cPanel service monitoring

If you prefer not to enable cPanel service monitoring for Dovecot in WHM, you may receive cPanel emails informing you that the service is unmonitored. For more information on cPanel service monitoring, see our article A Closer Look at cPanel Notifications.

Step #3: Check SSL settings

In certain cases, the SSL certificate previously applied to Courier may not automatically be applied to Dovecot. You can check the service’s SSL status by selecting Manage Service SSL Certificates from the left menu in WHM.


If you see certificate information listed next to Dovecot Mail Server, you don’t need to do anything else.

However, if you do not see certificate information listed next to Dovecot Mail Server, you may click the link named Apply Certificate to Another Service next to any of the other cPanel services in the grid, and then check the box next to Dovecot Mail Server. Click the blue Install button at the bottom to apply the certificate to Dovecot.

What If You Want to Keep Courier?

If you prefer not to switch to Dovecot and would like to continue to use Courier as your mail server, you will need to change your cPanel update preferences and select the LTS (long-term support) release tier.

By doing so, cPanel/WHM will not automatically update to the latest version, and you will be able to continue to use Courier for as long as cPanel supports your current release version. You also should no longer receive daily emails about the issue.

Note: Until you switch the mail server to Dovecot, cPanel will not be able to update beyond its current version.


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