You don't have to move your domain to us to use our email hosting. There are two ways to connect it; pick whichever suits you.
Option 1 — point the whole domain at us (simplest). At your registrar, set the nameservers to ns1.ukbox.host and ns2.ukbox.host. We then manage all the DNS, and SPF, DKIM and DMARC are set up automatically. If your website is hosted somewhere else, tell us where and we'll add the record that keeps it pointing there.
Option 2 — keep DNS where it is, add our mail records. Open a ticket and we'll send the exact records: an MX record pointing at your mail server, an A record for mail.yourdomain.co.uk, and the SPF and DKIM records that keep your mail out of spam. Add them at your DNS provider and mail starts arriving here as soon as they're live — usually within the hour.
Already receiving email somewhere else on this domain? Have us copy the old mailboxes across before the records change, so nothing is left behind. That's part of the free migration.