The recommended settings of the parameters are:
For a pure Internet (RFC0822) MTA:
AllowSourceRouting NO
InEnvelopAddressesBangIs IGNORED
For an Internet -> UUCP gateway MTA:
AllowSourceRouting YES
InEnvelopAddressesBangIs INTERPRETED
For a UUCP MTA (hypothetical case, given that avgated is a SMTP daemon ; this could occur if the UUCP rmail would inject the emails thru SMTP into avgated for virus checking):
AllowSourceRouting YES
InEnvelopAddressesBangIs INTERPRETED
However, all depends on the processing done by the forward MTA.