On 7/6/2012 8:43 AM, Paul M. Beck wrote:
> We have run into an issue with a large ISP indicating that SPF records should only use ~all and never -all
> Has anyone found -all to be problematic?
>
> Paul
>
-all means this is an exclusive list of where legit email can come 
from.  Unless you have 100% control over your users, they will use 
whatever/where ever to send email and you will run afoul of this one.

Lyle