[emojiSpam]

I have never received any important email with emoji in the subject. Actually, I find them so unprofessional that I send them straight to spam.

[Izkata]

Not just unprofessional, actual spam is the only place I've ever seen this. It's the clearest signal to me to delete without reading.

[OCISLY]

Good point. If someone sends you valuable information, he don't have to try to steal your attention with such cheap tricks.

[scintill76]

Counterpoint: eBay order updates use emoji in the subject. I don’t necessarily like it, but it could be considered important email.

[OCISLY]

I don't use eBay, so I don't know how these mails looks, but I bet they treat it as a marketing opportunity.