Not sure if this is the correct place to ask on this.

I am on a solaris 9.

We are using postfix for our email.

the standard email statement is:
mailx -s "subject" receiver.id < mail.text

I had to replace the sensitive data below but these are the messages.

Our servers are only allowed to send out, not receive, that is why the domain is unknown.

My questions are:
1. how do I trace the messages to the sender ? nothing seems to match to my tracelogs of my scripts that run on a scheduled basis. Mostly looked at PID.
2. Any idea what the error is? maybe its something simple... (i hope)

In my /var/adm/messages I am seeing:
May 10 12:00:29 MYSERVERID postfix/sendmail[21712]: [ID 947731 mail.crit] fatal: USERID.01(15482): Error writing message file
May 10 18:16:57 MYSERVERID postfix/sendmail[15193]: [ID 947731 mail.crit] fatal: USERID.01(15482): Error writing message file

In my /var/log/syslog I am seeing corresponding errors:

May 10 12:00:21 MYSERVERID postfix/qmgr[18326]: [ID 197553 mail.info] 908303744: from=<USERID.01@MYSERVERID.unknown>, size=1014, nrcpt=1 (queue active)
May 10 12:00:23 MYSERVERID postfix/smtp[21628]: [ID 197553 mail.info] 908303744: to=<custome.service@company.domain.name>, relay=mailhub.xxx.com[159.82.80.106], delay=2, status=sent (250 2.0.0 j4AG0M905217 Message accepted for delivery)
May 10 12:00:29 MYSERVERID postfix/sendmail[21712]: [ID 947731 mail.warning] warning: premature end-of-input on /usr/local/sbin/postdrop -r while reading input attribute name
May 10 12:00:29 MYSERVERID postfix/sendmail[21712]: [ID 947731 mail.crit] fatal: USERID.01(15482): Error writing message file


May 10 18:16:57 MYSERVERID postfix/sendmail[15193]: [ID 947731 mail.warning] warning: premature end-of-input on /usr/local/sbin/postdrop -r while reading input attribute name
May 10 18:16:57 MYSERVERID postfix/sendmail[15193]: [ID 947731 mail.crit] fatal: USERID.01(15482): Error writing message file
May 10 18:16:59 MYSERVERID postfix/pickup[11319]: [ID 197553 mail.info] 80200373F: uid=71 from=<lp>
May 10 18:16:59 MYSERVERID postfix/cleanup[13188]: [ID 197553 mail.info] 80200373F: message-id=<20050510221659.80200373F@MYSERVERID.unknown>
May 10 18:16:59 MYSERVERID postfix/qmgr[18326]: [ID 197553 mail.info] 80200373F: from=<lp@MYSERVERID.unknown>, size=1293, nrcpt=1 (queue active)