Postfix smtp mail to external hosts not possible

Solution 1:

Sep  5 09:19:22 myhostname postfix/smtpd[9086]: NOQUEUE: reject: RCPT from isp-ip.net[123.456.789.123]: 554 5.7.1 <[email protected]>: Relay access denied; from=<[email protected]> to=<[email protected]> proto=ESMTP helo=<thunderbird>

Try to emulate smtp session via telnet and add the output to the question. Also you can use swaks, it's just a perl script

# swaks -s isp-ip.net --helo thunderbird --to [email protected] --from [email protected] --auth PLAIN --auth-user [email protected] --auth-password 7654321 --auth-hide-password

Host did not advertise authentication

it seems that relay host doesn't support authentication. May be it does, but only over encrypted channel. Try to use 465/587 ports instead, for e.g.

# swaks -s isp-ip.net -tlsc -p 465 --helo thunderbird --to [email protected] --from [email protected] --auth PLAIN --auth-user [email protected] --auth-password 7654321 --auth-hide-password

# swaks -s isp-ip.net -tls -p 587 --helo thunderbird --to [email protected] --from [email protected] --auth PLAIN --auth-user [email protected] --auth-password 7654321 --auth-hide-password