MAIL
You can use NOTES.INI settings to limit the amount of memory used by open notes. The memory values are shared and maintained by mailbox event generation and any open router note.
For the following two NOTES.INI settings, RouterMaxEventMemorySizeBytes and RouterMaxEventMessageSizeBytes, if either of the maximum values specified are reached, the router falls back and searches mailboxes for new messages. New messages located during the search are not cached in the main message queue.
RouterMaxEventMemorySizeBytes
RouterMaxQueueMemorySizeBytes