This Post will show you the absolute easy way to fix the MMS settings on iPhone 3gs jail broken and unlocked for T mobile.
In brief, within your jail-broken iPhone, you must find the root file named com.apple.mms_override.plist, and edit it with a new code. Because its a root file, you must download and use iFile.
Using you Jail-broken iPhone go to :
1. Go to Cydia
2. Manage
3. Go to Sources
4. Click on Edit
5. Click on Add
6. Type in " http://cydia.xsellize.com, and click Add Source
7. Now, Go to Search and type in iFile
8. Install iFile from xSellize, because its free, otherwise BigBoss charges $4.
Using IFile
Navigate to
/Private/var/mobile/library/references.
Open com.apple.mms_override.plist and replace the code.(ClickText view and edit)
Copy the following code and Past it over the old code.
<?xml version="1.0"
encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
<key>MMS</key>
<dict>
<key>GroupModeEnabled</key>
<false/>
<key>MMSC</key>
<string>http://mms.msg.eng.t-mobile.com/mms/wapenc</string>
<key>MaxMessageSize</key>
<integer>1048576</integer>
<key>MaxRecipients</key>
<integer>10</integer>
<key>MaxVideoBitrate</key>
<integer>131072</integer>
<key>Proxy</key>
<string>216.155.165.50:8080</string>
<key>UAProf</key>
<string>http://www.apple.com/mms/uaprof.rdf</string>
<key>UserAgent</key>
<string>SonyEricssonW800i/R1L</string>
</dict>
</dict>
</plist>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
<key>MMS</key>
<dict>
<key>GroupModeEnabled</key>
<false/>
<key>MMSC</key>
<string>http://mms.msg.eng.t-mobile.com/mms/wapenc</string>
<key>MaxMessageSize</key>
<integer>1048576</integer>
<key>MaxRecipients</key>
<integer>10</integer>
<key>MaxVideoBitrate</key>
<integer>131072</integer>
<key>Proxy</key>
<string>216.155.165.50:8080</string>
<key>UAProf</key>
<string>http://www.apple.com/mms/uaprof.rdf</string>
<key>UserAgent</key>
<string>SonyEricssonW800i/R1L</string>
</dict>
</dict>
</plist>
click save and reboot iPhone
And That is It!