Emails from server no longer delivered correctly - after outsourcing email handling to Google Apps

Version: Virtualmin Pro 3.56

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Background:
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1. We do not use our own server as a name server/DNS. We use EveryDNS.net for DNS instead.

2. Emails were previously handled by our server/Virtualmin Pro.

3. Recently, we have decided to "outsource" our email handling to Google Apps (Gmail).

http://www.google.com/a/help/intl/en/users/gmail.html

Reasons:
(A) Reduce load on our server; no longer needs to handle emails
(B) Google Apps standard edition is free.
(C) Gmail has better SPAM/virus filtering system

4. The change is easy. Simply change the DNS records for mail server from

Priority 5 mail.mydomain.com

to

Priority 10 ASPMX.L.GOOGLE.COM
Priority 20 ALT1.ASPMX.L.GOOGLE.COM
Priority 20 ALT2.ASPMX.L.GOOGLE.COM
Priority 30 ASPMX2.GOOGLEMAIL.COM
Priority 30 ASPMX3.GOOGLEMAIL.COM
Priority 30 ASPMX4.GOOGLEMAIL.COM
Priority 30 ASPMX5.GOOGLEMAIL.COM

5. Emails to our mailboxes (now handled by googlemail.com) are received fine as long as they are not sent from our server/Virtualmin Pro.

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Problem:
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All emails sent from
(A) online forms on our websites
(B) Usermin i.e. http://www.mydomain.com:20000
(C) Webmin > Servers > Read User Mail
DO NOT reach its intended recipient email address (e.g. me@mydomain.com).

Instead they are bounced back to the virtual server's default user account i.e. mydomain.com@myserver.com

How can I solve this?

Status: 
Closed (fixed)