One of the key tasks facing the administrator of an in-house email server is filtering out spam emails. The harm caused by spam is both clear and significant: aside from posing a threat to the company's information security, it occupies space on the server's hard drive and reduces employee productivity when it appears in the 'Inbox.' Separating unwanted mail from business correspondence is not as simple as it may seem at first glance. The fact is that there is no solution that guarantees a 100% success rate in filtering out unwanted emails, and a poorly configured spam detection algorithm can cause the company much more harm than the spam itself.
In the Zimbra Collaboration Suite, spam protection is implemented using the freely available software package Amavis, which employs SPF, DKIM, and supports black, white, and gray lists. In addition to Amavis, Zimbra uses the ClamAV antivirus and the SpamAssassin spam filter. As of today, SpamAssassin is the optimal solution for spam filtering. Its operation principle is that each incoming email is checked against regular expressions characteristic of unwanted messages. After each triggered check, SpamAssassin assigns a certain number of points to the email. The more points accumulated by the end of the check, the higher the likelihood that the examined email is spam.
This scoring system for incoming emails allows for quite flexible filter configuration. In particular, it is possible to set a point threshold at which an email will be deemed suspicious and sent to the 'Spam' folder, or to establish a point threshold at which an email will be permanently deleted. By configuring the spam filter this way, two issues can be addressed: first, to prevent valuable disk space from being filled with useless spam messages, and second, to significantly reduce the number of business emails missed due to the spam filter's operations.
The main problem that Russian users of Zimbra may encounter is the built-in anti-spam system's unpreparedness for filtering Russian-language spam out of the box. The reason lies in the absence of built-in rules for Cyrillic text. Western colleagues solve this issue by unconditionally deleting all emails in Russian. Indeed, very few sane and sober-minded individuals would try to conduct business correspondence with European companies in Russian. However, users from Russia cannot afford such a solution. Partially solving this problem may involve adding , although their relevance and reliability cannot be guaranteed.
Due to its widespread adoption and open-source nature, the Zimbra Collaboration Suite can integrate other solutions, including commercial ones, for information security. However, the most optimal option might be a cloud-based cyber threat protection system. Configuring cloud protection typically occurs on both the service provider's side and the local server side. The essence of configuration is that the local address for incoming mail is replaced with the address of the cloud server, where emails are filtered, and only those emails that pass all checks are directed to the company's address.
Such a system is connected through a simple replacement of the IP address of the POP3 server for incoming mail in the MX records of the server to the IP address of your cloud solution. In other words, if the MX record of the local server looked something like this:
domain.com. IN MX 0 pop
domain.com. IN MX 10 pop
pop IN A 192.168.1.100
After replacing the IP address with the one provided by your cloud security service provider (let's assume it will be 26.35.232.80), the record will change to the following:
domain.com. IN MX 0 pop
domain.com. IN MX 10 pop
pop IN A 26.35.232.80
During the configuration in the personal account of the cloud platform, you will also need to specify the domain address from which unfiltered emails will arrive, and the domain address to which filtered emails should be sent. After these actions, the filtering of your email will occur on the servers of a third-party organization, which will take responsibility for the security of incoming mail at the enterprise.
Thus, the Zimbra Collaboration Suite is perfectly suited for both small businesses needing a cost-effective yet secure email solution and larger enterprises focused on continuously reducing the risks associated with cyber threats.
For all inquiries related to Zextras Suite, you can contact the company's representative, Katerina Triandafili, at katerina@zextras.com.
Source: habr.com
