function protonmail(domain, verification, dkim)
  -- Configure mail records for protonmail
  
  -- Verification
  txt(domain, "protonmail-verification=" .. verification)
  
  -- MX records
  mx(domain, "mail.protonmail.ch", 10)
  mx(domain, "mailsec.protonmail.ch", 20)
  
  -- SPF
  txt(domain, "v=spf1 include:_spf.protonmail.ch mx ~all")
  
  -- DKIM
  -- TODO: use concat()?
  cname("protonmail._domainkey", "protonmail.domainkey." .. dkim .. ".domains.proton.ch.")
  cname("protonmail2._domainkey", "protonmail2.domainkey." .. dkim .. ".domains.proton.ch.")
  cname("protonmail3._domainkey", "protonmail3.domainkey." .. dkim .. ".domains.proton.ch.")
  
  -- DMARC
  txt("_dmarc", "v=DMARC1; p=quarantine")
end

function vanityns(ns1, ns2)
  -- Configure vanity DNS nameservers

  aaaa(concat(ns1, "ns"), "2001:67c:25a0::1")
  a(concat(ns1, "ns"), "185.142.218.1")
  aaaa(concat(ns2, "ns"), "2001:67c:25a0::2")
  a(concat(ns2, "ns"), "185.142.218.2")
end