I'm having a few issues sending email from our mail server. Most seem to work, but some addresses are getting picked up as Junk/Unsafe.
We run our own mail server sitting on Ubuntu on IP 192.168.0.9, and on this mail server(Zimbra) we have approx 15 different domains for sending emails.
Our emails are then send from our server, via our fibre router(so via the external IP of the router).
Our external IP's RDSN resolves to mail.ourmaindomainname.com which we want it to.
All of our domain names(hosted on a different external web server) have A records and MX records.
e.g if we had test-domain.co.uk the following occurs:
MX points to mail.test-domain.co.uk and the A record (mail.test-domain.co.uk) points to the external ip address of our email server, which is what we need it to be.
Any suggestions how I can work out whats going on, or how I can stop these being picked up by spam/junk etc?
I've seen one thing, on mxtoolbox, whereby I did an SMTP test, and it says: Warning - Reverse DNS does not match SMTP Banner
I think this could be because i'm sending from say test-domain.co.uk but the server is setup to ourmaindomainname.com but as we only have 1 IP address, I need the rdns to be from mail.ourmaindomainname.com
Thanks for the help