Solaris

banner test > /tmp/test
ROOT@fcivra: /usr/lib/sendmail -v cdunavent@yahoo.com < /tmp/test
cdunavent@yahoo.com... Connecting to mailhost. via relay...
220 smtpirv.verizon.com ESMTP Sendmail 8.13.3/8.13.3; Wed, 20 Dec 2006 07:01:36 -0600 (CST)
>>> EHLO fcivra.
250-smtpirv.verizon.com Hello [156.145.240.238], pleased to meet you
250-ENHANCEDSTATUSCODES
250-PIPELINING
250-8BITMIME
250-SIZE 50000000
250-DSN
250-DELIVERBY
250 HELP
>>> MAIL From:<root@fcivra> SIZE=184
250 2.1.0 <root@fcivra>... Sender ok
>>> RCPT To:<cdunavent@yahoo.com>
250 2.1.5 <cdunavent@yahoo.com>... Recipient ok
>>> DATA
354 Enter mail, end with "." on a line by itself
>>> .
250 2.0.0 kBKD1aUD019624 Message accepted for delivery
cdunavent@yahoo.com... Sent (2.0.0 kBKD1aUD019624 Message accepted for delivery)
Closing connection to mailhost.
>>> QUIT
221 2.0.0 smtpirv.verizon.com closing connection

from your output it shud be going out as it is showing that it is able to connect to mailhost server.

cdunavent@yahoo.com... Connecting to mailhost. via relay...
220 smtpirv.verizon.com ESMTP Sendmail 8.13.3/8.13.3; Wed, 20 Dec 2006 07:01:36 -0600 (CST)
>>> EHLO fcivra.
250-smtpirv.verizon.com Hello [156.145.240.238], pleased to meet you

hmm ...

ok you do this, logon to the mailhost server(telnet to it) do a tail -f /var/log/syslog

then open another telnet session to the problem server and run the sendmail command again and see if you getting any errors from the syslog on mailhost.