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What
makes e-mails bounce? 
In
computer jargon, a bounced e-mail is one that never arrives in the recipient's
inbox and is sent back, or bounced back, to the sender with an error message
that
indicates to the sender that the e-mail was never successfully transmitted.
But
what happens when someone sends an e-mail out into cyberspace, and why
do e-mails sometimes bounce back? When
a user attempts to send an e-mail, he is telling his e-mail system to look for
the domain of the recipient (for example, webopedia.com) and the domain's mail
server. Once the e-mail system makes contact with the recipient's mail server,
the
mail server looks at the message to determine if it will let the message
pass through
the server. If the recipient's server has predetermined that
it is not accepting e-mails
from the sender's address (for example, if it
has blocked the address for anti-spamming
purposes), the server will reject
the message and it will subsequently bounce back
to the sender. The message
will also bounce back to the server if the mail server on
the recipient's
end is busy and cannot handle the request at that time. When an
e-mail is
returned to the sender without being accepted by the recipient's mail
server,
this is called a"hard bounce". Once
the e-mail has been accepted by the recipient's mail server there are still ways
for the message to be rejected. The mail server has to determine if the recipient
actually
exists within its system and if that recipient is allowed to accept
e-mails. If the recipient's
address does not exist on the mail server, then
the message will be rejected because
there is no one to deliver the message
to. If the sender misspells the recipient's address
then the system will recognize
this as a nonexistent address and bounce the message back.
If the recipient
exists but does not have enough disk space to accept the message
(i.e., if
his e-mail application is filled to storage capacity) then the message will bounce
back to the sender. Some mail systems predetermine a maximum message size that
it will accept and will automatically bounce the message if it exceeds that size
and
some mail systems predetermine a maximum amount of disk space the user
is allowed
to occupy on the server. When an e-mail is returned to the sender
after it has already
been accepted by the recipient's mail server, this is
called a "soft bounce". Occasionally,
a network failure at the sender or recipient end will cause an e-mail
to bounce
back to the sender. Typically, a bounced e-mail returns to the sender
with
an explanation of why the message bounced.
From
... PCWebopaedia.com
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