550 5.7.1 Access to not allowed by rules
SMTP Error Codes
Server blocked user access by a blacklist filter/rule, or server blocked access from the originating server by HELO/EHLO Filter.
Review server black list filters and user rules or set a bypass item. Whitelist the originating server in HELO/EHLO filter, or remove it from blacklist, or create a Bypass.
Applies To
SMTP Error Codes
See Also