572 and 550 RFC delivery status notification: The setting of the From Address are incorrect and/or an attempted was made to deliver but there was a non fatal error and it will be retried and/or some change to the message destination must be made for successful delivery View the list of RFC error return codes
Most ISP mail server have some requirements for outgoing or return REPLY TO email addresses as well as performing a reverse nslookup to prevent and disallow you to send emails to another ISPs SMTP mail server.
If the sender or recipient is a non-local user and to protect the mail server from being used by spammers to relay their messages by using another company’s network and computer resources. See: Blacklist
IP addresses are allocated to companies and
ISPs in blocks. Anyone can find out who administers a block of addresses or
the owner of a domain address by using an IP Block
whois tool to query the Internic database.
(Domain Name System) is a distributed
domain based naming system database that can be query to identify administers
of IP Address--which is a string of numbers, example:
220.127.116.11 are translated into a
string of "letters" called Domain Name
When we send an email we uses character string to specify a destination, like; 2service @ mailsbroadcast.com but the machine on the internet does not understand this name (character string).
The machine uses a protocol called IP (internet protocol) and numbers like these; 18.104.22.168 to represent a destination, which is not very user friendly, therefore, a special internet service called DNS (Domain Name Service) is to help convert character string (name) into numbers.
Every email domain or website URL has their own individual destination number that is different from another.
Therefore, we send an email to your local ISPs mail server, they will also have a local DNS (Domain Name Service) server (sort of like a mirror DNS site) that can be queried, identify and locate the actual destination of a character string (name).
Anyone can use a DNS Program query tool freeware from samspade.org to access a DNS Name Server on the Internet and gather data in its DNS database.
Many ISP filters incoming emails and automatically delete mails where the TO address is different from the actual recipient address-delete not bounced-hence you won't know if the message actually got to the intended recipient. See: Email Filtering
Notes: If you are using your own mail server program See: Mail Server FAQs