[Motorola Droid RAZR] fujcru:
rmusman, your problems may be due to problems in the APN settings. As you may have noticed, the APN settings on the various CM based KitKat ROM's all seem to be locked down and you can't change then once the ROM has loaded. I've noticed that the APN settings from my stock system are different from the APN settings the CM uses. I haven't had any problems sending or receiving SMS and MMS but I also merged the APN settings from my stock ROM to those in SlimKat before I flashed the ROM. And I am also on Verizon. I did notice that the APN settings from the stock side are different in relation to MMS so it is very possible that it is simply different APN settings that determine whether or not MMS works on the stock messaging apps.

Here's a look at the stock APN settings which pertain to Verizon:

<apn carrier="Verizon Internet" numeric="310004" mcc="310" mnc="004" apn="VZWINTERNET" mmsc="http://mms.vtext.com/servlets/mms" type="default,mms,dun,stdhipri,supl" />
<apn carrier="Verizon FOTA" numeric="310004" mcc="310" mnc="004" apn="VZWADMIN" type="fota" />
<apn carrier="Verizon IMS" numeric="310004" mcc="310" mnc="004" apn="VZWIMS" type="ims" />
<apn carrier="Verizon CBS" numeric="310004" mcc="310" mnc="004" apn="VZWAPP" mmsc="http://mms.vtext.com/servlets/mms" type="cbs,hipri" />
<apn carrier="Verizon 800" numeric="310004" mcc="310" mnc="004" apn="VZW800" type="vzw800" />
<apn carrier="Verizon Internet" numeric="311480" mcc="311" mnc="480" apn="VZWINTERNET" mmsc="http://mms.vtext.com/servlets/mms" type="default,mms,dun,stdhipri,supl" />
<apn carrier="Verizon FOTA" numeric="311480" mcc="311" mnc="480" apn="VZWADMIN" type="fota" />
<apn carrier="Verizon IMS" numeric="311480" mcc="311" mnc="480" apn="VZWIMS" type="ims" />
<apn carrier="Verizon CBS" numeric="311480" mcc="311" mnc="480" apn="VZWAPP" mmsc="http://mms.vtext.com/servlets/mms" type="cbs,hipri" />
<apn carrier="Verizon 800" numeric="311480" mcc="311" mnc="480" apn="VZW800" type="vzw800" />

And here are those same settings from SlimKat v3.2:

<apn carrier="Verizon" mcc="310" mnc="004" apn="internet" type="default,mms,dun" mmsc="http://mms.vtext.com/servlets/mms" protocol="IPV4V6" />
<apn carrier="Verizon Internet" mcc="310" mnc="004" apn="VZWINTERNET" type="default,dun" protocol="IPV4V6" roaming_protocol="IPV4V6" />
<apn carrier="Verizon FOTA" mcc="310" mnc="004" apn="VZWADMIN" type="fota" protocol="IPV4V6" roaming_protocol="IPV4V6" />
<apn carrier="Verizon IMS" mcc="310" mnc="004" apn="VZWIMS" type="ims" protocol="IPV4V6" roaming_protocol="IPV4V6" />
<apn carrier="Verizon CBS" mcc="310" mnc="004" apn="VZWAPP" type="cbs,mms" mmsc="http://mms.vtext.com/servlets/mms" protocol="IPV4V6" roaming_protocol="IPV4V6" />
<apn carrier="LTE - Verizon Internet" mcc="311" mnc="480" apn="VZWINTERNET" type="default,dun" protocol="IPV4V6" roaming_protocol="IPV4V6" bearer="14" />
<apn carrier="LTE - Verizon FOTA" mcc="311" mnc="480" apn="VZWADMIN" type="fota" protocol="IPV4V6" roaming_protocol="IPV4V6" bearer="14" />
<apn carrier="LTE - Verizon IMS" mcc="311" mnc="480" apn="VZWIMS" type="ims" protocol="IPV4V6" roaming_protocol="IPV4V6" bearer="14" />
<apn carrier="LTE - Verizon CBS" mcc="311" mnc="480" apn="VZWAPP" type="cbs,mms" mmsc="http://mms.vtext.com/servlets/mms" protocol="IPV4V6" roaming_protocol="IPV4V6" bearer="14" />
<apn carrier="LTE - Verizon SUPL" mcc="311" mnc="480" apn="VZW800" type="supl" protocol="IPV4V6" bearer="14" />

As you can see, there are some differences. I'm generally on LTE and you can see where the LTE - Verizon Internet from SlimKat makes no mention that that connection should handle MMS and doesn't have that mmsc reference. So adding the settings from the stock side might just make your SlimKat installation work just like your stock side.