Update v-add-mail-domain (#4027)

bin/v-add-mail-domain

@@ -16,7 +16,7 @@ domain=$2
 antispam=${3-yes}
 antivirus=${4-yes}
 dkim=${5-yes}
-dkim_size=${6-1024}
+dkim_size=${6-2048}
 restart="$7"
 reject=${8-no}