With an expression being neutral not a blank one. And the tone is mild-mannered not emotionless. Not that the person never says it more cheerfully. Do you have to always say it enthusiastically?
(Been told by a couple of family members a couple of times I should smile when I've said it, one finding it funny laughing a bit how I said it which made me privately annoyed when I was being nice. I feel self conscious after if I say it sometimes without smiling and I realise oh I have to remember next time I really don't want to feel daft again)