[Serusers] forward to PSTN

[Juha Heinanen]

Ri Liang writes:

 > When a particular user (for example 123 at foo.bar)  need to call to PSTN, we
 > need to sent in the "From" part as 456 at foo.bar, because the PSTN provider
 > needs the 456 to authenticate.

this comes up almost every week on the mailing list. please check the
archives.  the sort answer is: add rpid header instead of modifying
from and ask your pstn provide to use rpid instead.

-- juha