For all domains which we run a secondary DNS you may configure a MX fallback in your zone.

yourdomain.ch. IN MX 50 fallback.ip-plus.net.

Mail Relay: If your mailsystem is unable to send mail directly to any non local receipient you may configure mailout.ip-plus.net as your mailrelay. Please note, that we will relay mail only if we also run a secondary DNS for this domain.

Please make sure to replace all old entries "ubnsrv.unisource.ch" or "mailhost.ip-plus.net" with "fallback.ip-plus.net".