Additional Block Reasons

• Fatal Errors (IP blocked with all email from this server refused):
• 550 Access Denied. A previous user of this server triggered USA.NET automated spam controls. This results in an temporary automated block of the IP address to interrupt the spam delivery.


• Non-Fatal Errors (specific connections from an IP address blocked with only specific email refused):
• 501 Mail not allowed from localhost.localdomain. Please refer to http://postmaster.usa.net for an explanation.
  (This failure denotes an invalid hostname was received as the EHLO/HELO command during the SMTP conversation. The hostname must be a Fully Qualified Domain Name (FQDN)). Click here for instructions.
• 501 Mail not allowed from (xxxxx). Please refer to http://postmaster.usa.net for and explanation.
  (This falure denotes a blocked hostname was received as the EHLO/HELO command during the SMTP conversation) Please click to request removal.
• 501 MailFromRequiredDnsDomain. Invalid sender domain (ie: sksjdjsksj.com)
  (The sender's domain name does not have a DNS record. The domain name must have at least an A record for email to be accepted. Please, contact Support or the email administrator for this domain for assistance.)
• 501 Invalid host name appsvr.D_ULOP.PHILA.org.
  (This failure denotes the hostname received as the EHLO/HELO command during the SMTP conversation is invalid per RPC's. Please, contact postmaster here for assistance.

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