>[оверквотинг удален]
> Oct 21 12:59:58 gsm postfix/smtpd[96941]: connect from unknown[192.168.99.99]
> Oct 21 12:59:58 gsm postfix/smtpd[96941]: 60B0E5C045: client=unknown[192.168.99.99]
> Oct 21 12:59:58 gsm postfix/cleanup[96944]: 60B0E5C045: message-id=<05478AAA4A94447BB98B5943CA2777EF@gsm.net>
> Oct 21 12:59:58 gsm postfix/qmgr[96385]: 60B0E5C045: from=<root@gsm.net>, size=1466,
> nrcpt=1 (queue active)
> Oct 21 12:59:58 gsm postfix/smtpd[96941]: disconnect from unknown[192.168.99.99]
> Oct 21 12:59:58 gsm postfix/pipe[96946]: 60B0E5C045: to=<netmask@gsm.net>, orig_to=<38000XXXXX@gsm.net>,
> relay=smstools, delay=0.13, delays=0.11/0.01/0/0.01, dsn=2.0.0, status=sent (delivered
> via smstools service)
> Oct 21 12:59:58 gsm postfix/qmgr[96385]: 60B0E5C045: removed

Честно говоря не настраивал... Как вариант sendsms запускали от root-a, а в main.cf user=smstools. Прав на /dev/cuaxxx хватает?