Error In Sending Mail. Details: Mailbox Unavailable. The Server Response Was 5.7.1. Clinet Does Not Has Permission To Send As This Sender

     1. Create an Exchange mailbox for SMTP authorization. For example, app.mailing@domain.com

     2. Go to Home » System Configuration » Emails Configuration » Email Delivery Settings

1. Enter Internal/external IP of Edge/HUB server in SMTP server field.
2. Enter 25 in port number field. Enter 995 in port number field if it is being protected.
3. Turn on SMTP server requires authentication.
4. Enter app.mailin@domain.com in SMTP user name field and provide its password.

Go to Home » System Configuration » Emails Configuration » Email Templates and specify the ‘to’ and ‘from’ email addresses along with relevant fields. 

IMPORTANT: You should ensure that app.mailing@domain.com can send email as your sales/support account. For example, if your support account is support@oxyhosting.com and you want to send emails using app.mailing@domain.com then it should have Send As permission on support@oxyhosting.com account.

1. Start the Exchange Management Console.
2. In the console tree, click Recipient Configuration.
3. In the result pane, select the mailbox (support@oxyhosting.com in our example) for which you want to grant the Send As permission.
4. In the action pane, under the mailbox name, click Manage Send As Permission. The Manage Send As Permission wizard opens.
5. On the Manage Send As Permission page, click Add.
6. In Select User or Group, select the user (app.mailing@domain.com in our example) to which you want to grant the Send As permission, and then click OK.
7. Click Manage.
8. On the Completion page, the Summary states whether the Send As permission was successfully granted. The summary also displays the Exchange Management Shell command that was used to grant the Send As permission.
9. Click Finish.