Crashmail event buffer overflowed,

[gstrat88]

supervisor: 3.2.0
superlace: 1.0.0

configuration
[eventlistener:crashmail]
command=/usr/local/bin/crashmail -a -m xxx@xxx.xxx-o "Server %(host_node_name)s"
events=PROCESS_STATE_EXITED

Crashmail works ok for me but syslog keeps writing this message:

ERRO pool crashmail event buffer overflowed

I tried changing different stuff like buffer_size etc but non of them worked

Any idea?
Thanks!