I also have two domains and one server and both have different title, login theme and company logo. Here is my setup
1. Select a theme with its own logo (i.e. lemongrass, wave, tree, lake)
2. Change the company logo for each theme and use the COS settings to dedicate a specific theme for each domain.
3. Now, browse each company domain by using this URL.
Note: Zimbra server hostname = zimbra.company1.com
4. Here is my DNS setup:
Company 1
A: zimbra.company1.com xxx.xxx.xxx.xxx
MX: 10 zimbra.company1.com company1.com
Web Forward: mail.company1.com =
company1.com - Company Resources and Information. This website is for sale!
cloak: yes
title: Company 1 Web Client Log In
Company 2
A:
MX: 10 zimbra.company1.com company2.com
Web Forward: mail.company2.com =
company1.com - Company Resources and Information. This website is for sale!
cloak: yes
title: Company 2 Web Client Log In
Company 1 users will be access =http://mail.company1.com
Company 2 users will be access =http://mail.company2.com
Optional: You can create a vritual host for company2.com in the Admin Console so that users may not need to include @company2.com when typing their username in the log in screen.
PS: All of my zones where hosted at zoneedit. My Zimbra server uses live IP with firewall enabled.