Update SMTP server address

Hello,

I inherited the administration of a site which is already running nicely in production.
I need to do a simple update, which is to modify the settings for our SMTP server which has moved to a new address.

How can I change this setting ? The only options I have found would be to install a new plugin, but I would prefer not to install anything new as this would require a review from our security team.

Thanks for any help !