Hi Stephen,
I get them too.
I see it on some notifications when received on my normal email.

Martin555.

Dodgy Geezer is on the right track. It's an emoji converted to plain text. I have looked it up, it's the GB flag. Where do you see it? I've occasionally seen it in emails, but that'll be down to the email client. Not everywhere supports emojis and so it happens sometimes that you see the nonsensical characters behind them.

Stephen

This might help - but you're on your own if you want to look it up any further....