ASP Jmail Issues

Can anyone please help me with this. I have same code to send the emails. But once in a while i am getting this error messages. Could you please tell me what might be the possible reasons that makes this occur.

jmail.SMTPMail error '8000ffff'

503 must have sender and recipient first


Here are the program details:
Procedure call

SendEmail "survey@hotmail.com", "chads@hotmail.com", "", "", "Survey", myBody

Procedure

sub SendEmail(strFrom, strTo, strCc, strBcc, strSubj, strMsg)
dim oMail

set oMail = Server.CreateObject("JMail.SMTPMail&quot

oMail.Sender = strFrom

if StrHasValue(strTo) then
oMail.AddRecipient strTo
end if

if StrHasValue(strCc) then
oMail.AddRecipientCC strCc
end if

if StrHasValue(strBcc) then
oMail.AddRecipientBCC strBcc
end if

oMail.Subject = strSubj
oMail.Body = strMsg
oMail.Execute
Set oMail = nothing
end sub

You are getting error messages once in a while? Is there anything different about entries that cause the error compared to entries that work?

No. They get values from the database and database doesnt have null values for this field.