Problem with replacing default email app

[bdbull]

I've replaced the default email app with a version that allows me to change the port number to connect to my business' exchange server. It works fine unless I reboot. When I reboot, it drops the default port and won't allow me to add it back. I have to reinstall the new apk to get it to accept the port number again. What do I need to do to keep the OS from reverting back to the old (default) behavior when I reboot?