It explain in the guide. Is all through the ovh relay fw the encrypted messages to your npub. Try to send me a message from any email server to pub1lxktpvp5cnq3wl5ctu2x88e30mc0ahh8v47qvzc5dmneqqjrzlkqpm5xlc@uid.ovh

Don't forget to add in settings the bridge https://image.nostr.build/eb3b8a018e7ee46ebe780717b8246b8361f49803c1a8c4175caf1e4df52b4861.png