For those of you who are running jailbreaked iPhone's running on the iOS4 may have been experiencing MMS / APN issues, well the latest version Redsn0w puts an end to that and it works.

The latest redsn0w beta should fix any APN or MMS issues that users were seeing. It’s safe to re-run it on an already jailbroken iPhone without restoring…just deselect “Install Cydia” if you do that.

Instructions to jailbreak iPhone 3G and iPod touch 2G on iOS 4 using Redsn0w 0.9.5 as usual are exactly similar to the last release. If your phone is already jailbroken, just deselect “Install Cydia” option and re-run the jailbreak. Please read all the instructions posted here carefully before upgrading and jailbreaking your phone on iOS 4.

Once you have jailbroken your phone, you can unlock it using ultrasn0w 0.93 (on any baseband), guide for which is posted here.

iOS4 Download link

Redsn0w 0.9.5b5-5 for MAC

Redsn0w 0.9.5b5-5 for Windows

iTunes 9.2 for Windows and MAC

Source: RedmondPie