To enable MMS and Tethering, you might have to install a carrier-specific file for your carrier.

Details

If you look at the .ipcc-file you'll notice that it's a standard ZIP archive. Inside you'll find a folder Payload and a folder with your carrier's name. There you'll find a file carrier.list along some others. It is an XML file with all the features for your carrier. Some interesting snippets:

{% highlight xml %}
    <key>AllowEDGEEditing</key>
    <true/>
    <key>AllowMMSCEditing</key>
    <true/>
    <key>AllowMMSEditing</key>
    <true/>

...

ShowCallForwarded
    <false/>
    <key>ShowCallForwarding</key>
    <false/>
    <key>ShowTTY</key>  <!-- Show options for TTY devices -->
    <false/>

...

SupportMMS
    <true/>

...

SupportsNITZ