The onstat -g ntm option prints network mail statistics.
IBM Informix Dynamic Server Version 10.00.UC1 -- On-Line -- Up 01:57:33 -- 101376 Kbytes global network information: #netscb connects read write q-free q-limits q-exceed alloc/max 3/ 3 0 0 0 1/ 1 135/ 10 0/ 0 2/ 0 Network mailbox information: box netscb thread name max received in box max in box full signal 5 c631028 tlitcppoll 10 0 0 0 0 yes 6 c63e548 tlitcplst 10 0 0 0 0 no