diff --git a/src/mail.js b/src/mail.js
index b773b8760..4cb953d5e 100644
--- a/src/mail.js
+++ b/src/mail.js
@@ -581,13 +581,13 @@ function createMailConfig(mailFqdn, mailDomain, callback) {
         }
 
         // create sections for per-domain configuration
-        mailDomains.forEach(function (domain) {
+        async.eachSeries(mailDomains, function (domain, iteratorDone) {
             const catchAll = domain.catchAll.map(function (c) { return `${c}@${domain.domain}`; }).join(',');
             const mailFromValidation = domain.mailFromValidation;
 
             if (!safe.fs.appendFileSync(path.join(paths.ADDON_CONFIG_DIR, 'mail/mail.ini'),
                 `[${domain.domain}]\ncatch_all=${catchAll}\nmail_from_validation=${mailFromValidation}\n\n`, 'utf8')) {
-                return callback(new BoxError(BoxError.FS_ERROR, 'Could not create mail var file:' + safe.error.message));
+                return iteratorDone(new BoxError(BoxError.FS_ERROR, 'Could not create mail var file:' + safe.error.message));
             }
 
             const relay = domain.relay;
@@ -603,11 +603,13 @@ function createMailConfig(mailFqdn, mailDomain, callback) {
 
             if (!safe.fs.appendFileSync(paths.ADDON_CONFIG_DIR + '/mail/smtp_forward.ini',
                 `[${domain.domain}]\nenable_outbound=true\nhost=${host}\nport=${port}\nenable_tls=true\nauth_type=${authType}\nauth_user=${username}\nauth_pass=${password}\n\n`, 'utf8')) {
-                return callback(new BoxError(BoxError.FS_ERROR, 'Could not create mail var file:' + safe.error.message));
+                return iteratorDone(new BoxError(BoxError.FS_ERROR, 'Could not create mail var file:' + safe.error.message));
             }
-        });
+        }, function (error) {
+            if (error) return callback(error);
 
-        callback(null, mailInDomains.length !== 0 /* allowInbound */);
+            callback(null, mailInDomains.length !== 0 /* allowInbound */);
+        });
     });
 }