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when a user sends an email.. what is the procedures that is happening? i mean how the servers is distinguishing between and for example? are there special configuration has to be done in the DNS server?

thank you.

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up vote 11 down vote accepted

There are special DNS entries called MX Records that mail servers or mail transfer agents use to determine where to deliver mail for a domain.

Using as an example:       MX preference = 5, mail exchanger =       MX preference = 10, mail exchanger =       MX preference = 20, mail exchanger =       MX preference = 30, mail exchanger =       MX preference = 40, mail exchanger =

The MX record preference determines the server which will be tried first in order of lowest number to highest. So in this case mail servers will attempt to deliver mail to before trying etc.

If MX preference numbers are the same then the mail servers should randomly distribute mail between them.

With respect to mail it self the protocol used is Simple Mail Transfer Protocol or SMTP.

Connecting to webservers via HTTP uses DNS A records (or sometimes CNAME that point to A records) instead:       internet address =       internet address =       internet address =
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also note that in the absence of any MX records, the A records for the domain will be treated as an "MX 0" record. – Alnitak Nov 28 '09 at 17:50

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