Anti-spam/anti-virus filtering¶

CRIANN operates a cluster of anti-spam/anti-virus filtering servers that redirect accepted emails to the services that host mailboxes.

Incoming email management is done in stages:

• checking the reputation of the IP of the machine that contacted our service
• filtering by anti-spam and anti-virus engines
• routing of the email to the service that hosts mailboxes

Reputation check¶

The cluster uses a centralized database to protect our service from IP addresses considered to be sending SPAM or malware. You can check the reputation of an IP address via this service at the following URL: SenderBase

It is possible, upon request to our support, to add whitelisted IP addresses.

Filtering rules¶

An anti-spam filtering rule is applied, for each domain, from the following list of rules:

• SPAM and SUSPECTED SPAM erased / MARKETING tagged: SPAM and suspected SPAM are deleted and marketing emails have their subjects prefixed
• SPAM erased / SUSPECTED SPAM and MARKETING tagged: SPAM is removed and emails suspected of being SPAM or marketing emails have their subjects prefixed
• SPAM erased / SUSPECTED SPAM tagged: SPAM is deleted and emails suspected of being SPAM have their subjects prefixed
• SPAM and SUSPECTED SPAM tagged: SPAM and emails suspected of being SPAM have their subjects prefixed
• SPAM tagged (header): an X-Spam-Status: yes email header is added in case of detected SPAM

The incoming email, once the anti-spam filtering is done, goes through the antivirus engine.
After anti-spam and anti-virus filtering, our servers redirect the emails to the designated server in charge of mailboxes (on CRIANN service or external ones).

Redirection after processing¶

The emails, once processed, are retransmitted by the boxes to their final destinations using the following addresses:

• 193.52.218.20 (a1.relay.syrhano.net)
• 193.52.218.30 (b1.relay.syrhano.net)

We can apply static routing to one or more destinations (IP addresses or FQDN) or perform dynamic routing by consulting a remote LDAP service containing the information.