The error is telling you that the domain has no email delivery records in DNS. This doesn't seem to be the case any more though so you should no longer be seeing this error. Perhaps the owner of the domain made some DNS changes recently that took a while to propagate?
>nslookup -type=mx yesrecruit.co.uk 126.96.36.199 Server: cdns01.plus.net Address: 188.8.131.52 Non-authoritative answer: yesrecruit.co.uk MX preference = 10, mail exchanger = mx01.1and1.co.uk yesrecruit.co.uk MX preference = 10, mail exchanger = mx00.1and1.co.uk mx01.1and1.co.uk internet address = 184.108.40.206 mx00.1and1.co.uk internet address = 220.127.116.11 mx01.1and1.co.uk internet address = 18.104.22.168 mx00.1and1.co.uk internet address = 22.214.171.124
Bob Pullen Plusnet Products Team If I've been helpful then please give thanks ⤵