i've installed successfully and use the package esmtp
it is not an email (or smtp) server but it is a smtp relay client.
with esmtp you can send mails using your already existing email account with any provider which allows smtp
you can install it with "ipkg install esmtp"
then you need to edit the file /opt/etc/esmtprc with your account infos
after that you can use it like sendmail
example: sending a mail to
user@mail.com, note the two "\n\n" before the Message text !!