it is clear to me that both NetManage and Sun Mailtool is buggy.
(as if that helped....)
You didn't quote version numbers; I would suggest that any owners
of NetManage or Sun Mailtool on the list contact you for a sample
message, and report the bug to their respective vendors.
After all, commercial software should give you the right to
complain about it to the vendor when it doesn't support the standard
that it claims to support.
Wednesday night, in Stockholm, noticing that nobody else answered your
mail on the list, and just wanting to make supportive noises.
Harald T. Alvestrand