I am having a very hard time setting up Mail Server to my Ubuntu 18 server. I installed Mail Server from the app store. Setup a subdomain (mail.my_domain.com), MX, TXT, and added a user.
I verified that all 3 of the services are running, I verified the 25 port, even pkilled it and restart all services (Dovecot, Opendkim, Postfix).
But yet I am unable to send and receive the emails. If I send an email to GMAIL, it gives this error:
The IP you're using to send mail is not authorized 550-5.7.1 to send email directly to our servers. Please use the SMTP relay at 550-5.7.1 your service provider instead. Learn more at 550 5.7.1 https://support.google.com/mail/?p=NotAuthorizedError v65si5387427wmb.83 - gsmtp (in reply to end of DATA command))
And if I send email to my Namecheap Shared hosting email id, it gives this:
to=bixxxxni@stxxxxxxel.io, relay=mail.stxxxxxxel.io[1xx.5x.11x.2xx]:25, delay=22, delays=0.01/0.01/22/0.26, dsn=5.0.0, status=bounced (host mail.stxxxxxxel.io[1xx.5x.11x.2xx] said: 550 Access denied - Invalid HELO name (See RFC2821 4.1.1.1) (in reply to MAIL FROM command))
Even, I am unable to receive email to my aaPanel Mail server.
Kindly, guide me through.