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13.9 "Antispam" service configuration
Mail antispam or spam filter is a program for detecting and filtering unwanted e-mail messages that can come
through corporate mail servers and public e-mail services (spam, mail phishing, etc.).
The main task of the "Anti-spam" service is to detect such unwanted emails while they are still being delivered
to the recipient's mailbox. For this purpose, the ESR service router with configured "Antispam" service is
installed in the network in front of the protected mail server and redirects e-mail between this server and other
mail servers on the Internet through itself, actually performing the function of Mail Proxy.
Emails from external email domains will be analyzed in the Antispam service in the following ways:
authentication of the sending domain via SPF;
verification of the signature of an email signed with a domain key using DKIM technology;
identification of e-mails according to DMARC technology;
checking if there is a correct MX record for the domain from which the email is sent;
searching for the sender of an email in a list of known broadcast services;
searching for the sender of a letter in the RBL;
analysis of SMTP commands correctness during SMTP session pickup;
analysis of Unicode encodings present in the text of the letter;
analysis of references in the text of the email to phishing.
Emails that do not pass most of the checks will be discarded and will not reach the protected mail server.
13.9.1 Basic configuration algorithm
Step Description Command Keys
1 Configure router network name. esr(config)# hostname <NAME> <NAME>- up to 64 characters.
2 Assign domain name for the router. esr(config)# domain name
<NAME>
<NAME>- up to 255 characters.
3 Assign DNS server IP address used for
DNS names resolution.
esr(config)# domain name-server
<IP>
<IP> – in the format of
AAA.BBB.CCC.DDD, where each
part takes values from 0 to 255.
4 Enable DNS name resolution. esr(config)# domain lookup enable
5 Create an "Antispam" service profile esr(config)# security antispam
profile <NAME>
<NAME>- up to 31 characters.
6 Set the description of the "Antispam"
service profile (optional).
esr(config-antispam-profile)#
description<DESCRIPTION>
<DESCRIPTION> – up to 255
characters.
When using the "Antispam" service to protect the mail server, make a number of additional settings
not directly related to the ESR router configuration.
1) Change the MX record for the domain in use so that it does not point to a protected mail server,
but to the ESR IP address with the "Antispam" service configured.
2) Configure the mail server to use SMTP Proxy, where the Proxy will be ESR with the "Antispam"
service configured.
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