Not a LISTSERV problem, but ....

We run LISTSERV ( with SMTP and LMAIL ) under VMESA

I'm suddenly seeing more than one site ( incl AOL ) rejecting mail due
to envelope problems !  Is this an anti-spam/anti-relay technique
recently implemented ?  ( I THOUGHT we were fully RFC821/822 compliant ! )
Is this an parm-controlable option in our SMTP ?  Any pointers/comments
greatly appreciated !
                                                            - mike
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Note: delivery error converted to LMail format at CNSIBM.ALBANY.EDU.

--> Error description:
Error-For:  [log in to unmask]
Error-Code: 3
Error-Text: 553 <@CNSIBM.ALBANY.EDU:[log in to unmask]>...
        Source routed envelope sender rejected (See RFC 822, section 6.2.7)

Error-End:  One error reported