DKIM, SPF, and DMARC Protection

Plesk supports a number of anti-spam solutions for validation of mail
messages identity:

• DKIM (DomainKeys Identified Mail) is a method
  used to associate a domain name identity with an outgoing message and
  to validate a domain name identity associated with an incoming
  message through cryptographic authentication.
• SPF (Sender Policy Framework) is a method used
  to prevent sender address forgery, i.e. using fake sender addresses.
  It allows mail server to check that incoming mail from a domain comes
  from a host authorized by that domain’s administrator. In addition,
  Plesk uses SRS (Sender Rewriting Scheme), so
  that forwarded messages can pass SPF checking.
• DMARC (Domain-based Message Authentication,
  Reporting and Conformance) is a technology to extend the capabilities
  of the SPF and DKIM methods. The DMARC policy defines how the
  receiver should treat email messages depending on the results of DKIM
  and SPF checking.

The mail server requirements for these solutions are as follows:

In this table, ‘+’ means that the solution is supported by all versions
that are supported by Plesk
Obsidian.
‘-‘ means that the solution is not supported.