Certificate problem during migration

[neontangerine]

After going live and moving some users over to Zimbra I am having a problem which I believe is due to my certificate. I have an odd situation where I have installed Zimbra to reflect the setup I intend to have in a couple of weeks and as a result have a naming conflict with my certificate.

I currently have my email going to Google using the name 'mail.mydomain.com' and have installed Zimbra with the server name 'mail.mydomain.com' and have setup a catchall domain 'mydomain.ca' so I can receive emails. I have configured users in Google to forward their email to 'username@mydomain.ca' and this is working very well for receipt. For connecting to my server I have aliased 3 names to my server; webmail.mydomain.com, smtp.mydomain.com, and imap.mydomain.com which all work very well, from the internet and internally on my LAN.

My problem seems to be with clients, webbrowsers, and mobile devices. My certificate shows it is from 'mail.mydomain.com' but of course the connection is from 'webmail.mydomaincom' and from the imternet if anything does a lookup of that name it shows the google IP. I have been able to tell Firefox, Thunderbird, and the iPhone ot accept and trust this certifcate anyhow and all is fine for those devices. Anything else (Blackberry, MS Explorer) only trusts the cert for that session and does not make this persistent.

I am expecting that once I have everyone moved over and can have all my DNS point to my Zimbra server that this should go away. IS there anything I can do for now so the certificate would show itself as 'webmail.mydomain.com' or ideally as an alias to 'mail.mydomain.com'?

I looked in the forums for something similar but did not find anything that helps, or I missed something. Any help or suggestions would be appreciated, I am not an SSL certificate expert by any stretch.

[neontangerine]

Perhaps to make things easier what I think I ideally need is a way to have a certificate that is valid for the following names, all for a single server;

mail.mydomain.com
webmail.mydomain.com
smtp.mydomain.com
imap.mydomain.com

Can this be done with a single certificate or do I need to create 4 separate certificates?

Alternatively is it possible to have the certificate reflect the IP and not the name of the server?

Your help and guidance is appreciated.