Setting IMAP session limits

You can set limits on IMAP sessions by setting the maximum number of IMAP sessions, or by setting a default timeout value

Specifying the maximum number of IMAP sessions

About this task

To maintain a session with a client, Domino® allocates a main session thread, which uses a certain portion of the server's memory. Each IMAP client connecting to the server consumes an additional session thread, and thus a certain amount of memory. If the number of IMAP sessions exceeds the amount of available memory, the server can become unstable.

To ensure that servers can properly support the number of connecting IMAP clients, you can set a limit on the number of concurrent IMAP sessions allowed. By default, servers do not place limits on the number of concurrent IMAP sessions.

After the number of sessions reaches the specified limit, the IMAP service rejects additional connection attempts.

Specifying a default IMAP session timeout value

About this task

After a user opens a session with the IMAP service, the service waits for commands from the mail client. If no commands are received, the session is considered to be idle. Sessions that are idle for a long period may be the result of a user forgetting to log out after completing their mail processing. Because servers must allocate memory for each IMAP session and send periodic keep-alive messages to a client to maintain the connection, idle sessions represent a waste of server resources.

You can limit how long the server continues to maintain client sessions that do not show any activity. Specify the number of minutes that the IMAP service waits before disconnecting idle IMAP client sessions. Many IMAP clients poll for new mail every 10 minutes, so it's best to set the value to greater than 10 minutes, because the overhead of supporting an idle session is less than the overhead required to support clients logging in and opening mailboxes.

By default, servers drop idle sessions after 30 minutes.

To set IMAP session limits


  1. Make sure you already have a Configuration Settings document for the server(s) to be configured.
  2. From the Domino® Administrator, click the Configuration tab and expand the Messaging section.
  3. Click Configurations.
  4. Select the Configuration Settings document for the mail server or servers you want to restrict mail on, and click Edit Configuration.
  5. Click the IMAP > Basics tab.
  6. For the field Maximum number of IMAP sessions, enter the maximum number of concurrent IMAP client sessions the server allows. By default, no limit is imposed.
  7. For the field IMAP session timeout, enter the time, in minutes, that the IMAP service continues to maintain an idle session. If there is no client activity by the end of the specified time, Domino® closes the session. By default, servers drop idle sessions after 30 minutes.
  8. Save and close the document.