This is a sendmail question, not a perl question, <delete>but you seem to use your localhost machine as the smtp server, if you don't actually have an smtp server on your local machine, this will not work.</delete>

You probably need to change your sendmail config.

Update: ok so you try to connect to 'smtp.mydomain' - assuming this is the right smtp server name, the most likely explenation is that your stmp server is malfunctioning. Contact your system administrator or fix the smtp server yourself.

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Joost       downtime n. The period during which a system
            is error-free and immune from user input.
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