diff --git a/composer.json b/composer.json
index 72abce51..edba326f 100644
--- a/composer.json
+++ b/composer.json
@@ -30,7 +30,9 @@
         "psr/log": "For optional PSR-3 debug logging",
         "league/oauth2-google": "Needed for Google XOAUTH2 authentication",
         "hayageek/oauth2-yahoo": "Needed for Yahoo XOAUTH2 authentication",
-        "stevenmaguire/oauth2-microsoft": "Needed for Microsoft XOAUTH2 authentication"
+        "stevenmaguire/oauth2-microsoft": "Needed for Microsoft XOAUTH2 authentication",
+        "ext-mbstring": "Needed to send email in multibyte encoding charset",
+        "symfony/polyfill-mbstring": "To support UTF-8 if the Mbstring PHP extension is not enabled (^1.2)"
     },
     "autoload": {
         "psr-4": {