Very postfix was setup correctly to relay mail to other domain, by chatGPT

how to use telnet to very that postfix was setup correctly to send out mail to other domain ChatGPT To verify that Postfix is set up correctly to send mail to other domains using Telnet, you can follow these steps:

Check Postfix Configuration: First, ensure that Postfix is configured properly to send outgoing mail. Key configuration files for this purpose are typically located in /etc/postfix/. Important files to check include main.cf and master.cf. Verify DNS Configuration: Make sure that the DNS records for your domain are properly configured, including MX (Mail Exchange) records. Telnet to SMTP Server: Use Telnet to connect to the SMTP server of the recipient domain. The standard SMTP port is 25. You can use Telnet to connect to it like so: php Copy code telnet <recipient_domain> 25 Initiate SMTP Connection: Once connected, initiate the SMTP conversation by typing: Copy code EHLO yourdomain.com Check Response: After typing the EHLO command, you should receive a response from the SMTP server indicating that it is ready to start accepting commands. Send Test Email: You can then proceed to send a test email by typing the following commands: vbnet Copy code MAIL FROM: <your_email_address> RCPT TO: <recipient_email_address> DATA Subject: Test Email This is a test email. . Replace <your_email_address> with the sender's email address and <recipient_email_address> with the recipient's email address. Check Delivery Status: After sending the email, you should receive a response indicating whether the email was accepted for delivery. You may also want to check the mail logs on both the sender and recipient sides to verify the delivery status. Quit Telnet Session: To end the Telnet session, type: Copy code QUIT By following these steps and examining the responses from the SMTP server during the Telnet session, you can verify whether Postfix is set up correctly to send mail to other domains.

alexlai@nextcloud:~$ telnet localhost 25
Trying ::1...
Connected to localhost.
Escape character is '^]'.
220 nextcloud.yushei.com.tw ESMTP Postfix (Ubuntu)
EHLO yushei.me
250-nextcloud.yushei.com.tw
250-PIPELINING
250-SIZE 10240000
250-VRFY
250-ETRN
250-STARTTLS
250-ENHANCEDSTATUSCODES
250-8BITMIME
250-DSN
250-SMTPUTF8
250 CHUNKING
MAIL FROM: alexlai@yushei.me
250 2.1.0 Ok
RCPT TO: alexlai@munetaka.me
250 2.1.5 Ok
DATA
354 End data with <CR><LF>.<CR><LF>
Subject: 2024-04-25 08:06 test postfix relay
Hello
Hi
.
250 2.0.0 Ok: queued as 9E43D400E7B75
quit
221 2.0.0 Bye