mail: 'my' location is available as mail location

move the reserve domains check to app location validation code

src/apps.js

@@ -148,6 +148,7 @@ exports = module.exports = {
     _validatePortBindings: validatePortBindings,
     _validateAccessRestriction: validateAccessRestriction,
     _validateUpstreamUri: validateUpstreamUri,
+    _validateLocations: validateLocations,
     _translatePortBindings: translatePortBindings,
     _parseCrontab: parseCrontab,
     _clear: clear
@@ -1288,6 +1289,11 @@ async function validateLocations(locations) {
 
     const domainObjectMap = await domains.getDomainObjectMap();
 
+    const RESERVED_SUBDOMAINS = [
+        constants.SMTP_SUBDOMAIN,
+        constants.IMAP_SUBDOMAIN
+    ];
+
     for (const location of locations) {
         if (!(location.domain in domainObjectMap)) return new BoxError(BoxError.BAD_FIELD, `No such domain in ${location.type} location`);
 
@@ -1297,6 +1303,10 @@ async function validateLocations(locations) {
             subdomain = subdomain.replace(/^\*\./, ''); // remove *.
         }
 
+        if (RESERVED_SUBDOMAINS.indexOf(subdomain) !== -1) return new BoxError(BoxError.BAD_FIELD, `subdomain '${subdomain}' is reserved`);
+
+        if (dns.fqdn(subdomain, location.domain) === settings.dashboardFqdn()) return new BoxError(BoxError.BAD_FIELD, `subdomain '${subdomain}' is reserved`);
+
         const error = dns.validateHostname(subdomain, location.domain);
         if (error) return new BoxError(BoxError.BAD_FIELD, `Bad ${location.type} location: ${error.message}`);
     }