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(Redirected from Sender Verification)
The main mail protocol, SMTP has a hole in it: there is no verification of the sender. This allows spammers and others to pretend to be anyone they want. But with a little bit of effort, sendmail (for example) can be configured to use SSL and user verification. That way you can have your own SMTP-server accessible anywhere, without open relay.
There are also several new protocols for fixing SMTP problems:
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