sendmail-doc - 8.15.2-14~deb10u1 main

Sendmail is an alternative Mail Transport Agent (MTA) for
Debian. It is suitable for handling sophisticated mail
configurations, although this means that its configuration
can also be complex.
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Don't try anything fancy in sendmail without using this for guidance.
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Because of the complexity, you may find yourself wanting to peruse
the documentation files included herein. The main files are:
cf.README.gz -- A reference for all things in sendmail.{mc,cf}
op.{ps,txt}.gz -- The care and feeding of Sendmail.
faq.txt.gz -- Sendmail FAQ, current as of the package date.
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Other files include the references for smrsh and libmilter.