Patch to sender_permitted_from plugin to fix a crash with certain address and problems with MX secondaries

[Philip Gladstone]

Hi,

I attach a patch for

1)   In sender_permitted_from, fix a crash when sending mail to postmaster.
2)   In sender_permitted_from, fix a problem when mail is being sent to 
you from your MX secondary and you (incorrectly) deny it due to SPF 
filtering.

In http://pond.gladstonefamily.net/qp-spf.pf.txt

Happy holidays

philip