Works for me as well. Here's what I did differently.
1. Did not install BootNeuter.
2. Used ziphone 2.6 and put it on RECOVER instead of DFU
I believe BootNeuter is not needed because this particular custom ispw contains BootNeuter. Once iTunes was complete with its thing, BootNeuter automatically fired up and did its thing.
I told iTunes to do a restore and after which Mail doesn't work. But I've encountered this before in the past. Just do the following if you have the same problems.
1. ssh to iPhone
2. chown -R mobile:mobile /private/var/mobile
Mail app should work after that.
Yahoo push mail is still not working though.. It has never worked since day 1 for me. Have tried all the remedies out there (google it) but none of them worked.
When I tested it (sending from GMail to Yahoo Mail and vice versa from desktop), I could hear a chime after a few seconds, but the Mail icon on the springboard is still not showing anything
After a few minutes it shows as there's mail, but it was for the GMail account.
So, sad to say initial test is showing Yahoo push mail is not working.
Before I forget, I tried 2 other ipsw files and they did not work. iTunes error out with 1403 unknown error. This one worked.