These checkboxes select which protocols Dovecot will listen on.

Note: cPanel’s Webmail system requires IMAP in order to function.

Note: If you do not select a checkbox, the system will operate in authentication-only mode.

Note: LMTP is required and you cannot disable it.

This option allows you to enable Dovecot to listen for IPv6 Address requests.

Note: You must select a protocol in the Protocols Enabled section before selecting IPv6 Enabled.

This setting will allow remote email clients to authenticate using unencrypted connections. When set to “no”, only connections originating on the local server will be allowed to authenticate without encryption. Selecting “no” is preferable to disabling IMAP in the Protocols Enabled section since it will force remote users to use encryption while still allowing webmail to function correctly.

This setting allows the use of weak authentication hashing methods. When set to “No”, users can only use secure password hashes. Insecure password hashing methods leave users vulnerable to brute force attacks. Users that use these methods will not be able to log into their accounts until they change their password. Set this option to “Yes” to allow users that use weak password hashes to log in.

This is a standard format list of the SSL ciphers Dovecot should use. Typically this will only need to be adjusted for PCI compliance."

This value represents the minimum SSL protocol that Dovecot clients may use to connect. Typically, you will only need to adjust this value for PCI compliance.

This setting determines whether to include service subdomains in the list of SNI hostnames Dovecot recognizes. Disabling this setting may cause email users who configured their email clients to connect to IMAP or POP3 on this server using one of these service subdomains, instead of using the mail subdomain or the domain itself, to have verification issues when trying to connect securely. However, disabling this also will reduce the amount of memory Dovecot must set aside for remembering configuration information, which may resolve issues where Dovecot regularly exceeds memory limits, including some which are not currently configurable through this interface, when serving many thousands of domains through cPanel.

Specifies the maximum number of mail (IMAP and POP3 servers) processes that may be running at one time.

The maximum memory usage of the IMAP and POP3 processes, in MB. These processes read mostly memory-mapped files, so setting a high limit should not affect your server’s performance.

Specifies the number of simultaneous IMAP connections that a single user (IP address) may make from each IP address.

Specifies the number of minutes between IMAP IDLE “OK Still here” messages. Increasing this may help increase battery life for some mobile clients.

Specifies the number of simultaneous POP3 connections that a single user (IP address) may make from each IP address.

This specifies how many spare authentication processes should be kept running to listen for new connections.

Specifies the maximum number of authentication processes that may be running at one time.

The maximum memory usage of the IMAP and POP3 login processes, in MB.

The number of seconds to delay before moving users to the IMAP hibernate process. This will help save system memory. A value of “0” disables this option.

The master authentication process keeps a cache of validated logins so that it does not need to recheck the login credentials each time mail is retrieved. This specifies the amount of memory used for the cache, in MB.

The time, in seconds, that successful logins will be stored in the authentication cache. A lower value may cause more work for the authentication server but decrease the likelihood of problems when passwords are updated.

The time in seconds that failed logins will be stored in the authentication cache. Lowering this value may cause more work for the authentication server but decrease the likelihood of problems when passwords are updated.

Specifies whether to use a new login process for each new POP3 or IMAP connection. Setting this to yes may improve the security of the Dovecot authentication processes, but doing so imposes a significant performance penalty on heavily loaded servers.

The maximum memory usage (in MB) of Dovecot’s other internal services not covered by another setting. Each SSL/TLS certificate that Dovecot tracks requires additional virtual memory for all Dovecot internal services. Servers with many domains may need to increase this value to ensure that Dovecot operates correctly.

The time in seconds between updates to idle IMAP connections. Lowering this value will cause idle clients to see new messages faster, however lower values may also increase server load slightly. The default setting of 30 is recommended.

When this option is enabled, the system will count email messages in the Trash folder against the user’s quota. Note: In order to recalculate existing quotas, you must run the “/usr/local/cpanel/scripts/generate_maildirsize --allaccounts --confirm” command in a root shell after you modify this option.

When you enable this option, the system will compress recently created and delivered messages.

The compression level to save messages in when you enable “Compress Messages”.

When this option is enabled, the system will remove messages in the Trash and Deleted Messages folders based on the expiration time configured below.

The number of days to keep messages before the Auto Expunge Trash function removes them. This function only works if the Auto Expunge Trash function is enabled.

When this option is enabled, the system will remove messages in the Spam folder based on the expiration time configured below.

The number of days to keep messages before the Auto Expunge Spam function removes them. This function only works if the Auto Expunge Spam function is enabled.

The maximum size to which a MDBOX mailbox file may grow before the system rotates it.

The maximum time that an MDBOX mailbox file may exist before the system rotates it.

How Dovecot will respond when a system disk quota or mailbox disk quota prevents delivery:

Reject the message permanently. [ ? ] This option reduces mail overhead.

Defer delivery temporarily. [ ? ] This option allows the user time to reduce disk usage and to receive the message.

The minimum number of processes that the system will attempt to reserve in order to accept more client connections. A setting of 0 will only start the LMTP server when needed and will conserve memory.

The maximum number of LMTP server processes.

The maximum number of concurrent LMTP deliveries per user. A value of “0” disables the per-user limit.