Support toggling internal mail handling

email.go

@@ -154,6 +154,33 @@ func (c *UserContext) UpdateEmailAccount(emailAccount EmailAccount) error {
 	return nil
 }
 
+// UseInternalMailHandler tells the server to use the local mail handler for the given domain. If this is enabled, other
+// domains on the server that email this domain will use the server's local mail handler to deliver the email, rather
+// than looking up the domain's MX records. This is fine if your email is being hosted on the same server, but not
+// otherwise.
+func (c *UserContext) UseInternalMailHandler(domain string, enable bool) error {
+	var response apiGenericResponse
+
+	body := url.Values{}
+	body.Set("domain", domain)
+
+	if enable {
+		body.Set("internal", "yes")
+	} else {
+		body.Set("internal", "no")
+	}
+
+	if _, err := c.makeRequestOld(http.MethodPost, "API_DNS_MX?action=internal", body, &response); err != nil {
+		return err
+	}
+
+	if response.Success != "Option Saved" {
+		return fmt.Errorf("failed to set internal mail handler for %v: %v", domain, response.Result)
+	}
+
+	return nil
+}
+
 // VerifyEmailAccount (user) accepts the full email address as well as the password for the account. If the credentials aren't correct, an error will be returned.
 func (c *UserContext) VerifyEmailAccount(address string, password string) error {
 	var response apiGenericResponse

go.mod

@@ -5,6 +5,5 @@ go 1.22
 require (
 	github.com/goccy/go-json v0.10.3
 	github.com/google/go-querystring v1.1.0
-	github.com/spf13/cast v1.6.0
-	golang.org/x/text v0.15.0
+	github.com/spf13/cast v1.7.0
 )

go.sum

@@ -15,6 +15,6 @@ github.com/rogpeppe/go-internal v1.9.0 h1:73kH8U+JUqXU8lRuOHeVHaa/SZPifC7BkcraZV
 github.com/rogpeppe/go-internal v1.9.0/go.mod h1:WtVeX8xhTBvf0smdhujwtBcq4Qrzq/fJaraNFVN+nFs=
 github.com/spf13/cast v1.6.0 h1:GEiTHELF+vaR5dhz3VqZfFSzZjYbgeKDpBxQVS4GYJ0=
 github.com/spf13/cast v1.6.0/go.mod h1:ancEpBxwJDODSW/UG4rDrAqiKolqNNh2DX3mk86cAdo=
-golang.org/x/text v0.15.0 h1:h1V/4gjBv8v9cjcR6+AR5+/cIYK5N/WAgiv4xlsEtAk=
-golang.org/x/text v0.15.0/go.mod h1:18ZOQIKpY8NJVqYksKHtTdi31H5itFRjB5/qKTNYzSU=
+github.com/spf13/cast v1.7.0 h1:ntdiHjuueXFgm5nzDRdOS4yfT43P5Fnud6DH50rz/7w=
+github.com/spf13/cast v1.7.0/go.mod h1:ancEpBxwJDODSW/UG4rDrAqiKolqNNh2DX3mk86cAdo=
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=