When organizations begin using Outlook Web Apps, it's often only a matter of time before someone on the senior
management team asks if OWA can be branded with the corporate logo or colors. As long as you have a basic understanding of HTML and Cascading Style Sheets (CSS), Microsoft makes it easy to customize OWA 2013.
This tip focuses on OWA 2013's premium version, which supports customization; the light version doesn't support customizations that are based on OWA themes. You should be able to customize older versions of OWA in a similar manner, but you have to slightly alter the technique due to differences in file paths. This tip also assumes Exchange is configured using the default installation path.
Creating a theme in OWA 2013
Although you can technically get away with modifying existing OWA themes, it's smarter to build new themes. If you make a mistake when editing a default theme, you could irreparably damage OWA. Here we'll copy a default theme and use it as a starting point for customizing OWA
Log on to your Client Access Server (CAS) server and navigate to:
C:\Program Files\Microsoft\Exchange Server\V15\ClientAccess\OWA\<version>\Owa2\resources\Themes
Create a folder with the name of your organization, then copy the contents of the Base folder into that new folder.
Before you move on, there is an XML file you'll need to update. Go into the folder you just created and open the themeinfo.xml file. Locate the displayname value and change it to match the folder name. For example, I named my new theme folder "Posey," so I set the display name to "Posey" (Figure 1).
Figure 1. Set the display name to match the folder name.
Configure OWA to use your theme
Exchange Server 2013 allows users to change their theme at will. There are plenty of OWA themes from which users can choose. You can use PowerShell to set the default theme, but users will still be able to change themes.
Suppose you want to set the default theme to "Posey." The cmdlet to do so is:
Set-OWAVirtualDirectory –Identity "owa (Default Web Site)" –DefaultTheme Posey
If you want to force users to use the new theme, you'd modify the command slightly by appending the –ThemeSelectionEnabled parameter to the end of the command and setting the value to $False. The command would look like this:
Set-OWAVirtualDirectory –Identity "owa (Default Web Site)" –DefaultTheme Posey –ThemeSelectionEnabled $False
Once you've entered the appropriate command, you'll need to reboot the CAS server or reset the Internet Information Server using the IISReset /NoForce command.
Customize OWA themes
So far, we've created a duplicate theme and redirected user traffic to it. Next, you can modify the theme to meet your needs. It's a good idea to create the modifications on a lab server, then copy the files to the production environment once you're satisfied with the results.
The main file you'll want to edit is called Premium.css, which is located in the custom theme folder. This file controls the colors and fonts that OWA uses. Keep in mind this isn't the only CSS file Exchange uses; there are other CSS files the Exchange Control panel uses.
In addition to changing fonts and colors, you may want to change the logo or other graphical elements OWA uses; it uses many files in the Portable Network Graphics (PNG) format for multiple visual elements. You can edit these files, but be sure not to change any of the image dimensions.
Customizing the OWA sign-on page
The modifications discussed so far allow you to change the look and feel of an OWA session, but many organizations also want to change the OWA sign-on screen. You can change the colors and fonts the screen uses by going to:
C:\Program Files\Microsoft\Exchange Server\V15\FrontEnd\HttpProxy\owa\auth\<version>\themes\resources
Once there, edit the logon.css file. There are also PNG files located in this folder the sign-on page uses. Any of these files can be edited or replaced with custom images, but it's recommended you use the same image dimensions.
About the author:
Brien Posey is an eight-time Microsoft MVP for his work with Windows Server, IIS, Exchange Server and file system storage technologies. Brien has served as CIO for a nationwide chain of hospitals and health care facilities, and was once responsible for IT operations at Fort Knox. He has also served as a network administrator for some of the nation's largest insurance companies.