Receiving mail from account after disconnecting

I’m having an issue with an account that was added via pop3 a while ago. I disconnected the account some time ago but the emails are still arriving in the inbox of my main account.

As the account was added via pop3, it is deleting the emails from the hosting server.

The emails are still addressed to the correct account, and I have checked that there are no forwarding rules that would cause this.

I imagine I’m doing something incredibly silly, but I am at a total loss for why this is happening.

Any ideas?