Note that the address is not encoded or protected in any way from harvesting by spambots. For this, see the Secure From Spammers example.
<?php the_author_email(); ?>
Displays author email address as a "email@example.com" link.
<a href="mailto:<?php the_author_email(); ?>">Contact the author</a>
This example partially 'obfuscates' address by using the internal function antispambot() to encode portions in HTML character entities (these are read correctly by your browser). Note the example uses get_the_author_email() function, because the_author_email() echoes the address before antispambot() can act upon it.
<a href="mailto:<?php echo antispambot(get_the_author_email()); ?>">email author</a>
This tag does not accept any parameters.