The MailLeaveSessionsOpen setting in notes.ini can be used to improve router performance by avoiding constant creation and destruction of sessions. This is handy for servers that do a lot of internal mail routing. Leaving the sessions open will lower bandwidth as handshaking between servers no longer needs to happen for each session.
MailLeaveSessionsOpen=1 will leave all sessions open.
MailLeaveSessionsOpen=2 will leave all LAN based sessions open.
MailLeaveSessionsOpen=3 will not leave any session open.
The performance savings are greater when used on servers within a cluster.
When absent or set to 0, the default behavior is to leave no sessions open
Ensure that the MailLeaveSessionsOpen setting in NOTES.INI has a value of '1' (or at least '2').
Valid on all Domino platforms.
Valid for Domino versions 7.0 and beyond.
MailLeaveSessionsOpen is a router specific setting and does not interfere with the DB server specific setting Server_Session_Timeout, or visa versa.
Domino Configuration Tuner:
This setting is included in the DCT
catalog of best practices.