Ensure you have downloaded both Mozilla and AllPeers sources as described in Getting the Source.
export AP_WITH_OUTLOOK=1
AllPeers uses conditional compilation to build different XPIs for different deployment (testing version, rc version). The building is straightforward, take proper .mozconfig-* from superman module and copy it to your home or mozilla directory with name .mozconfig .
In order to reduce risk of using wrong configurations when working on both HEAD and Release Candidate branch, it is recommended to checkout HEAD branch of superman into mozilla/extensions/allpeers and the RC branch to mozilla/extensions/allpeers-rc. Use .mozconfig-*-rc to build the Firefox which will use the allpeers-rc directory instead of allpeers.
If you want to have GPL libraries enabled in your build (currently MFP), you can set AP_WITH_GPL_LIBRARIES to 1 in license.mk file in the root of AllPeers source directory. Notice, that product built in this way must be distributed under GPL license, because it contains GPL libraries (MPL and LGPL cannot be used).
After all previous steps are done, run:
make -f client.mk build #Your Mozilla is here /mozilla\_obj-browser-release/dist/bin/firefox.exe
Please refer to Mozilla's building documentation to get help in building mozilla.