Admin Email Not Updating

I’ve seen a couple of similar posts (here and here) about this issue, but not been able to resolve it based on their experiences.

We’ve just updated the admin email on our site (in general site settings, UM email settings and UM notification settings) but the emails are still coming through from the old admin address. Is there an amount of time that we need to wait for this setting to take effect (currently 3hrs post change) or is there something I’ve missed?

Thanks,

Al