MailRift puts real mailboxes on a domain you already own, with a full webmail client, calendar, contacts, forwarding and inbound routing. One subscription covers one domain and every mailbox on it, so the bill does not move when you add a colleague. From CHF 4.90 per month per domain, hosted entirely in Germany.
Three self-serve tiers, each priced per domain per month. Paying annually costs about 16% less.
Every account can run one free trial. MailRift creates a test subdomain under a domain you own and gives you one mailbox, 1 MB of storage and three outbound emails, so you can walk the whole setup before deciding. No credit card required.