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 (for example,
example_account@example_domain.com)
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
(for example,
others_account@example_domain.com) 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.
Some mail servers are programmed to accept incoming e-mails and store
them for further analysis without initially checking to determine if the
recipient exists or is even capable of receiving the message.
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 will returns to the
sender with an explanation of why the message bounced.
