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

• T-Mobile Germany: 24100.net
• the same file with more features enabled (see next section): Download here

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:

        <key>AllowEDGEEditing</key>
        <true/>
        <key>AllowMMSCEditing</key>
        <true/>
        <key>AllowMMSEditing</key>
        <true/>
...
        <key>ShowCallForwarded</key>
        <false/>
        <key>ShowCallForwarding</key>
        <false/>
        <key>ShowTTY</key>  <!-- Show options for TTY devices -->
        <false/>
...
        <key>SupportMMS</key>
        <true/>
...
        <key>SupportsNITZ</key>   <!-- Network Identity and TimeZone (time synching via carrier) -->
        <false/>Code language: HTML, XML (xml)

You can upload the .ipcc file using the Developer version of iTunes 8.2.0.10¹Or change the shortcut to iTunes so that it reads: ...\iTunes.exe" /setPrefInt carrier-testing 1, Mac users run defaults write com.apple.iTunes carrier-testing -bool TRUE. Or you can upload the file to a webserver and download it to your phone. There’s also the possibility of creating a single merged XML file which then must be sent using the MIME type application/x-apple-aspen-config.

MMS Settings

The carrier file for T-Mobile Germany doesn’t contain the MMS settings. So go to Settings → General → Network → Cellular Data Network and input the following under the MMS section:

• APN: mms.t-d1.de
• Username: t-mobile
• Password: mms
• MMSC: mms.t-mobile.de/servlets/mms
• MMS Proxy: 172.28.23.131:8008
• MMS Max Message Size: 300
• MMS UA Prof URL: <leave blank>

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  Or change the shortcut to iTunes so that it reads: ...\iTunes.exe" /setPrefInt carrier-testing 1, Mac users run defaults write com.apple.iTunes carrier-testing -bool TRUE