Signed Receipts using Outlook Express

While looking at the S/MIME ESS signed-receipt message generated using 
Outlook Express 5.0 on Windows 2000, I noticed that in the
' EncapsulatedContentInfo'  field of the CMS 'Signed-Data' ASN.1 structure, the
    eContent [0] EXPLICIT OCTET STRING
is instead encoded as a
    eContent [0] EXPLICIT SEQUENCE

Is this a known issue or am I mistaken ?

Thanks in advance,

Vamsi Motukuru