YES. I think usually the dedicate one radio to the uplink. The standard AP has two radios, by default one in 2.4GHz the other in 5GHz band. Not sure if newer Wifi standards offer more flexibility while keeping performance. Technical details.
But in general a „wireless bridge“ is a mode many devices support. GL.iNet did a great job to offer this very easy to use (hiding the OpenWRT away).
But you can also use two devices. A wireless bridge (L2) and a router of your choice.
A simple approach would be to just run an IMAP server. For receiving you use a script using POP3 to download newly arrived emails (which is run every 5 minutes for example). If your server is offline, nothing gets lost.
For the sending side you can either use your mail ISP’s SMTP server directly from the client or you install a local relay as a mitm to the ISP’s SMTP.