I trust you are well.
The SMTP status along with all other servers is (offline) regardless of the settings being correct. Yesterday I had the same issue with an iPhone and a restart of the phone solved the issue. The same applies to the Apple Macs, restarting the Mac results in mails being sent out. I'm not sure if there is a way to change it without restarting but if everything else fails and settings are correct, ask the client to restart the device.