You might be required to send mime email when you are sending mail message outside of lotus notes mailing system such as outlook , internet mails(Gmail , yahoo , etc) or any other 3rd party mail system. then you can use the below code to get better control different parameters
session.ConvertMIME = False
Set maildoc = New NotesDocument( currentDatabase )
maildoc.Form = "Memo"
Set body = maildoc.CreateMIMEEntity
Set header = body.CreateHeader({MIME-Version})
Call header.SetHeaderVal("1.0")
Set header = body.CreateHeader("Sender")
Call header.SetHeaderVal(sender ID)
Set header = body.CreateHeader("Principal")
Call header.SetHeaderVal(principal ID)
Set header = body.CreateHeader("From")
Call header.SetHeaderVal(From ID)
Set header = body.CreateHeader("Subject")
Call header.SetHeaderVal( Subject )
Set header = body.CreateHeader("Reply-To")
Call header.SetHeaderVal(reply ID)
Set header = body.CreateHeader("To")
Call header.SetHeaderVal(sendToString)
Set header = body.CreateHeader("Cc")
Call header.SetHeaderVal(copyToString)
Call stream.WriteText( bodyText )
Call body.SetContentFromText( stream, "text/html; charset=iso-8859-1", ENC_NONE )
session.ConvertMIME = True
session.ConvertMIME = False
Set maildoc = New NotesDocument( currentDatabase )
maildoc.Form = "Memo"
Set body = maildoc.CreateMIMEEntity
Set header = body.CreateHeader({MIME-Version})
Call header.SetHeaderVal("1.0")
Set header = body.CreateHeader("Sender")
Call header.SetHeaderVal(sender ID)
Set header = body.CreateHeader("Principal")
Call header.SetHeaderVal(principal ID)
Set header = body.CreateHeader("From")
Call header.SetHeaderVal(From ID)
Set header = body.CreateHeader("Subject")
Call header.SetHeaderVal( Subject )
Set header = body.CreateHeader("Reply-To")
Call header.SetHeaderVal(reply ID)
Set header = body.CreateHeader("To")
Call header.SetHeaderVal(sendToString)
Set header = body.CreateHeader("Cc")
Call header.SetHeaderVal(copyToString)
Call stream.WriteText( bodyText )
Call body.SetContentFromText( stream, "text/html; charset=iso-8859-1", ENC_NONE )
session.ConvertMIME = True