Mail on an extended network

You’ll want to discuss this network with the router vendor.

The default configuration for small networks has one IP router.

More than one router is possible, requires some IP setup including subnets, and requires multiple SSIDs.

Usual for these would be access points, or a mesh configurations. Both are “transparent” to IP networking. These “act like” an Ethernet patch cable. Both of these will use the same SSID(s) for the entire network, and clients can freely roam between the access points or mesh routers.

If your ISP router was not reconfigured as part of this (and if the same Wi-Fi hardware vendor is used for both boxes, it might do this reconfiguration automagically), then you’ll either end up with a different SSID on the two Wi-Fi boxes (which’ll probably work), or with a not-routing-at-all-well mess (which won’t work well).

The gear I usually use will automatically mesh among access points, which makes this easier to have an access point without a wired link.

But in any case, you’ll need the Wi-Fi extender to provide some assistance, or somebody to set up this configuration, or you’ll be learning more about Wi-Fi and wired and IP.