SMTP Simple mail transfer protocol
SMTP / Email spoof tests
Basic server test 2023 - https://ssl-tools.net/mailservers
Test mail - http://www.allaboutspam.com/email-server-test/ -> Send mail to "test @ allaboutspam.com"
Website check - https://www.amberloom.com/
2023-06 send test email to server https://www.wormly.com/test-smtp-server/
2023-06 apply to remove IP from https://www.spamrats.com/
Check / Removal spam lists
2023-06 Fixed https://spfbl.net/en/delist/ ==> check https://matrix.spfbl.net/103.252.118.112
- rbl.rbldns.ru
Verify smtp ssl/tls certificate
printf 'quit\n' | openssl s_client -connect mail.example.com:25 -starttls smtp | openssl x509 -dates -noout printf 'quit\n' | openssl s_client -connect smtp.vigor.nz:25 -starttls smtp | openssl x509 -dates -text | grep "verify\|notAfter=\|vigor\|SAN\|DNS:\|Subject Alternative Name:"
Debug smtp sasl starttls authentication
Connect and move to tls protected channel
$ openssl s_client -starttls smtp -crlf -connect vigor.nz:25 ehlo testconnection auth plain (base64encodedstring)
test sasl (/etc/sasldb2 )with
# sasldblistusers2 # testsaslauthd -u user -p password -f /var/spool/postfix/var/run/saslauthd/mux
add user to sasl
saslpasswd -c -u mail.example.com -a smtpauth test
view postfix smtp logs using journalctl
journalctl -u postfix@-.service -f
Check tls certificate on smtp server
# echo "quit" | openssl s_client -starttls smtp -crlf -connect <smtp.host>:25 | openssl x509 -noout -text | grep DNS:
...