Every organization needs internal smtp relay servers to send emails from printers, file servers & several other internal applications.  It’s implementation should be carefully planned and executed to have high-availability and security.

  1. Email sending applications based on their recipients are of three types :-
    1. Send email to internal email addresses only.
    2. Send email to external email addresses only.
    3. Send email to internal and external email addresses.
  2. Considerations :-
    1. Lock down smtp server access to certain senders.
    2. Configure High Availability of SMTP servers.
    3. Configure necessary logging of SMTP logs.
    4. Setup Monitoring.
  3. Products
    1. Exchange Online Protection
    2. Microsoft Exchange Server 2013
    3. Postfix
    4. IIS SMTP relay

I will explain in next article on how to use each product for different requirement.

Thank you for reading the article !