Make sure you have entered an Domain Name under Network -> iLO Dedicated Network Port -> General
Otherwhise your <Mail From> - Adress for AlertMail will look like <Hostname>.@<SenderDomain>
Note the point between <Hostname> and @, this will cause Exchange Servers (Exchane 2013) to discard Alert Messages from this sender.
If you enter an Domain Name it just works fine.
Your <Mail From> - Adress will look like <Hostname>.<DomainName>@<SenderDomain>...
Also make sure to use the IP-Adress instead of DNS-Name of the Mail-Server if you have not defined any internal DNS-Servers in Network -> iLO Dedicated Network Port - IPv4 Settings .