I made a .prg (and did some slight conversion to make a .vbs) and it looks like this. I can run this a zillion times and the mail gets there.

	oMsg = CreateOBject( "JMail.Message" )
	oMsg.Logging =  True
	oMsg.From = "mail@place.com
	oMsg.MailServerPassword = "pass"
	oMsg.MailServerUserName = "user"
	oMsg.FromName = "Steve Craft"
	oMsg.ReplyTo = "me@oh.my"
aa=	oMsg.AddRecipient( "aplace1.com" , "Stephen" )
bb=	oMsg.AddRecipient ( "aplace2.com" , "Dude" )
	oMsg.AddRecipientBCC("evenanotherplace@com.com")
	oMsg.Subject = "How are you?"
	oMsg.Body = "simple jmail stuff" 
cc=	oMsg.AddAttachment("c:\boot.ini") 
ff=	oMsg.AddHeader("Originating-IP","193.15.14.623")
dd=	oMsg.LogCustomMessage("Hello world")
*	StrToFile( oMsg.MailData , "maildata.txt")  &&  For debug
	oMsg.Silent = False
ee=	oMsg.Send( "ipname.of.mail.server" )

I have never seen your error messages, but the above works for me fine.