Merak Instant AntiSpam : Sender Policy Framework and Sender Rewriting Scheme


The development team of Merak Email Server by have implemented a useful and effective security feature - SPF technology.

SPF (Sender Policy Framework) is a security extension to the SMTP protocol preventing the email sender domain from being forged.

Full text

PRAGUE 09/06/2005: Under normal circumstances, an SMTP server will accept any email that is delivered to it, regardless of where it actually comes from, or where the Headers say it comes from. This helps spammers "spoof" email addresses - For example, you could receive a spam message selling Viagra that looks like it comes from your colleague at work. This is considered to be a security hole in SMTP and SPF is one of the most effective techniques to prevent this.

SPF technology allows the domain owner to add an additional DNS record for the domain, specifying which machines are authorized to send messages that report to be from this domain. Any SMTP server that is SPF compliant can check these records against the actual sending machine and decide whether to allow the message through.

Merak Email Server offers SPF technology as a part of the Merak Instant AntiSpam module, one of the most complete, and powerful, AntiSpam packages in the world.

An inherent problem of SPF is SMTP forwarding. When a server forwards a message without changing the "mail from" Header this new message could fail SPF checking. This is solved by implementing SRS (Sender Rewriting Scheme). SRS forces the rewriting of the "mail from" address by the forwarding server. Merak's AntiSpam module comes with SRS, for exactly this reason.

About IceWarp

IceWarp, Ltd. was started in 1999 with the development of Merak version 1. Merak’s exceptional product stability, performance and reliability quickly escalated its global adoption rate with ISPs and businesses. Over the years, IceWarp has maintained a technology leadership position by continuing to advance Merak through many industry-firsts, including:

  • First mail server supporting SSL
  • First mail server with Web mail
  • First integrated multithreaded antivirus
  • First integrated anti-spam
  • First GroupWare with API (ODBC based)
  • And now, the first server with integrated FTP and Web server capabilities.

Contact address

IceWarp Ltd. is located at City House, 6 Karaiskakis street, CY-3040 Limassol, Cyprus