IIS and Mail Server on same box?

I have a Windows 2012 web server. On it I have IIS and all my websites setup.

I installed a mail server on this same box. I set it up in the firewall to use allow TCP over these ports, etc. It is working fine.

But now all of my websites are stopped. I tried to start them again and get this error:
>>The process cannot access the file because it is being used by another process

I looked this up and found this:

It says it could be caused by this:
•Another process is using port 80 or port 443 on the computer that is running IIS. By default, IIS uses port 80 as the default TCP port and port 443 for Secure Sockets Layer (SSL).

Can a mail server and web server live on the same box? If so, how can I set them up to live nicely together?

This is Icewarp mail server and I am hosting on Rackspace if that helps. I also added a reverse DNS to the admin panel in Rackspace for the IP address and attached it to my mail server name: mail.blah.com

Starr DuskkASP.NET VB.NET DeveloperAsked:
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The Icewarp mail server started earlier than IIS did, and therefore it's IIS that's complaining.
Icewarp can be configured to use other ports (though IIS can do that too). Since Icewarp is for internal use and IIS is for world wide use, it's better to adjust Icewarp to use other ports, than the other way around.
It means, Icewarp users will use https://domain.com:8443/ for Icewarp, instead of the normal website users having to use strange different ports.
If that's NOT your intent (and Icewarp is the main site. then just turn around what I said, leave Icewarp as it is, change IIS).

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Starr DuskkASP.NET VB.NET DeveloperAuthor Commented:
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Microsoft IIS Web Server

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