smtp error 554 connection to server failed.

[viariemail]

Hi,
     I am facing issue sending emails, if use other machine in same network. please find the attached file.

See I have installed the Bitnami Roundcube in windows 2016 server, the same machine the email was sent successfully, but I have tried in different machine unable send email.

getting error : smtp error 554 connection to server failed.

How do I fix this issue? here with attached my configuration as well for your kind reference. please lookup and let me know.

I have tested the local users can send emails  to my office 365 online exchange server user, working fine .

but how get email from  my office 365 online exchange server user to my local roundcube email users? it's possible?

[viariemail]

Please find attached defaults.inc.php for your kind reference.

[JohnDoh]

I believe 554 means something went wrong during the SMTP transaction. You could enable smtp_debug and check that log for more info. Either way the error is coming from your SMTP server not from Roundcube.

If I had to guess I'd say its because you are trying to send emails from [email protected] which is obviosuly not valid and probably you are trigging from spam protection on your smtp server.