Gmail, Yahoo work but iCloud emails bounces with 503 5.5.1 Error: send HELO/EHLO first (in reply to RCPT TO command)

You can test via telnet.

SSH to your box and send test email to a real icloud recipient.

Read here: How to Test an SMTP Server with Telnet. Step-by-Step Tutorial

telnet mx01.mail.icloud.com
Or tail the mail log when sending from MIAB and paste here the response:

cat /var/log/mail.log | grep "postfix/smtp" | grep -P 'status='

1 Like