What are the common attack vectors for a Microsoft Exchange Server?
My online searches only yield discussion into various APT groups, and technical write-ups of different 0day exploits. There does not seem to be an OWASP top 10 vulnerabilities, nor any threats that appear to be commonly used.
Unless it is a common attack vector, side channel attacks (those involving measurements like timing) are outside the scope of my question.
This is not for academic research, so anything even partially reputable will be fine.