Why a core file is created whenever I send a mail in AIX

Whenever i send a mail like: mail <mail id>, a core file is created under /var/spool/mqueue/ path. This is increasing the space of the file system. Why is that core file get created. Does it happens normally. I am getting an errpt error as:
LABEL: CORE_DUMP
IDENTIFIER: B6048838

Date/Time: Thu 10 Aug 14:45:06 2006
Sequence Number: 18971
Machine Id: 00ac034df3493
Node Id: sreenath
Class: S
Type: PERM
Resource Name: SYSPROC

Description
SOFTWARE PROGRAM ABNORMALLY TERMINATED

Probable Causes
SOFTWARE PROGRAM

User Causes
USER GENERATED SIGNAL

    Recommended Actions
    CORRECT THEN RETRY

Failure Causes
SOFTWARE PROGRAM

    Recommended Actions
    RERUN THE APPLICATION PROGRAM
    IF PROBLEM PERSISTS THEN DO THE FOLLOWING
    CONTACT APPROPRIATE SERVICE REPRESENTATIVE

Detail Data
SIGNAL NUMBER
11
USER'S PROCESS ID:
1491156
FILE SYSTEM SERIAL NUMBER
4
INODE NUMBER
2093
PROCESSOR ID
1
CORE FILE NAME
/var/spool/mqueue/core
PROGRAM NAME
sendmail
ADDITIONAL INFORMATION
rightmost C
free_y 3BC

Symptom Data
REPORTABLE
1
INTERNAL ERROR
1
SYMPTOM CODE
PIDS/5765E6200 LVLS/520 PCSS/SPI2 FLDS/sendmail SIG/11 FLDS/rightmost VALU/c FLDS/free_y

Please help me in this problem.
Thanks,
Sreenath