If you have UFW running on your machine, then it means that all connections (except the ones you define) are going to be blocked.
So in order to ensure that SMTP plugin works, you have to ensure that you are allowing communications on the default SMTP ports. Now, I'm not quite sure which one of them is used by your plugin, but it should be one of these: 25, ...
You can have as many SMTP relays as you want and your email server separately working on another provider.
what matters is to have your SMTP relay server IP addresses in your DNS server(SPF Record) as a relay server to make sure your emails are delivered to Inbox.
Just to mention that, when you send emails via command, you don't need to have MX record ...
Finally I managed to set up my services. Here's few points you should care if you wish to set up yours.
Enable smtp_sasl_auth_enable and smtpd_sasl_auth_enable. I don't know why it is not enabled by default.
Set smtp_sasl_password_maps , so it knows where to find the password.
On roundcube, set tls:// prefix, and if using self signed certificate, set in smtp ...
Install one of them:
It will create a symlink from sendmail to msmtp, which will forward to any SMTP server you configure. Then configure RT to use sendmail.
This was a configuration problem in master.cf. The configuration shown above (in my question) only sets smtp_bind_address for inbound traffic, meaning for the listening daemons.
For outbound traffic, meaning when the postfix daemon sends mail to other servers, the following line in master.cf must also have the bind address specified. In the default/sample ...
In order to create projects you need resourcemanager.projects.create permission or roles/resourcemanager.projectCreator role.
Both can be granted by your organization admin like in this case.
To find out who is your Organization Administrator, open https://console.cloud.google.com/iam-admin/iam?project=YOUR_PROJECT_NAME
As mentioned by @Serhii, port 25 is ...
If it's a small business I would tend to cut over directly by changing the MX after prefeeding everyone mailbox PST content to O365 as you have less risk to loose a email in transit.
At the MX cut the Outlook client will stop getting new emails, but the users can use their O365 online via the Microsoft webpage to see their new emails for the time you connect ...
First, you need to add Partner Connector in the Office365 Exchange Admin center. Then add your server IP address there.
Now in your SendMail MTA Configuration add this
define(`RELAY_MAILER_ARGS', `TCP $h 25')dnl
define(`ESMTP_MAILER_ARGS', `TCP $h 25')dnl
define(`confAUTH_OPTIONS', `A p')dnl