Do not unescape %2C, %3B, %3D, or %40 in URI parameters, nor
%2C, %2F, %3B, %3D, or %40 in URI path.

The @ sign can be ambiguous in the SIP URL, e.g.,

<sip:test.info;p

darcs-hash:20070903141455-65a35-61e1bee07ac93f94b9b67e51ed18a4a7e8b8eaf3.gz