If you deleted the stock messaging app, you can do like I did to fix it. Note that you would be rooted to have done this in the first place and hopefully would know something about terminal emulator and making your system rewritable, etc.
1. Extract the Mms.apk file from the rom zip package (in system/data usually).
2. Place the Mms.apk file on the root directory of your sd card.
3. Using terminal emulator,
a. su (for root permission)
b. sysrw (or mount -o remount,rw -t yaffs2 /dev/block/mtdblock4 /system)
c. busybox cp /sdcard/Mms.apk /system/app/Mms.apk
d. busybox chmod 644 /system/app/Mms.apk (to change permissions like the rest of the programs in /system/app)
e. busybox rm /data/app/com.android.messaging-1.apk (to remove the mms installation from data if it is there...file may be named differently or may not be present)
f. sysro (or mount -o remount,ro -t yaffs2 /dev/block/mtdblock4 /system)
g. sync
h. exit
4. reboot.
This should install the mms program into the correct spot in your system for it to function with the right permissions. You can then go into messaging and turn off all notifications, hide the messaging icon if your launcher allows it, and send and receive MMS messages using Handcent without having to reinstall the entire ROM.
I do not claim to be the best at messing with ROMs or using terminal emulator, but I had deleted mms and decided to investigate how to fix it. I fixed it for my phone using the above method after some research. I do not use File Explorer and realize that there are several ways to accomplish the same thing. I hope this helps someone else.
