Add rule for email servers (SMTP)

Go to Firewall and select between IPv4 or IPv6 using the default filter.

Now, click +Add firewall rule and select Business application rule.

Specify the general rule details.

Application template

Select Email servers (SMTP) to configure a rule for SMTP based email applications.

Description

Specify the policy description.

Rule position

Specify the position of the rule.

Available options:

Top
Bottom

Rule group

Specify the rule group to add the firewall rule to. You can also create a new rule group by using Create new from the list.

If you select Automatic, the firewall rule will be added to an existing group based on first match with rule type and source-destination zones.

Rule name

Specify a name to identify the policy.

Specify Source details.

Source zones: Click to select the source zone. Click Add new item to define a new LAN or DMZ zone.
Allowed client networks: Select the allowed host(s) or add a new one by clicking Add new item.
Blocked client networks: Select the blocked host(s)/network(s).

Specify Destination & service details.

Destination host/network

Select the destination host/network to apply rule. It is the public IP address through which users access internal server/host over the internet.

Available options:

IP address: Specified IP address is mapped to a corresponding mapped single or range of IP addresses. If a single IP address is mapped to a range of IP addresses, the device uses a round robin algorithm to load balance the requests.
IP range: Specified IP address range is mapped to a corresponding range of mapped IP addresses. The IP range defines the start and end of an address range. The start of the range must be lower than the end of the range.
Interface IP: (Only available for IPv4). Select when any of the device port, alias or virtual LAN (VLAN) sub interface is required to be mapped to the destination host or network.

Forward type

Select the type of external port from the available options.

Available options:

Port
Port range
Port list
Everything

When Everything is selected, all ports are forwarded. Select other options to enable custom port forwarding and specify port forwarding details.

Service port(s) forwarded (not available if Forward type selected is Everything)

Specify the public port number for which you want to configure port forwarding.

Protocol (not available if Forward type selected is Everything)

Select the protocol TCP or UDP to be used by forwarded packets.

Specify Forward to details.

Protected server(s)

Select from the available options on which the email server is to be hosted.

Available options:

IP address: External IP address is mapped to the specified IP address.
IP range: External IP address range is mapped to the specified IP address range.
IP list: External IP address is mapped to the specified IP list.
FQDN: (Available only for IPv4 virtual hosts). External IP address is mapped to the specified FQDN. Internal mapped server can be accessed by FQDN.

Mapped port

Specify mapped port number on the destination network to which the public port number is mapped. Mapped port must have the same number of ports as specified in the public service, or at least have one port. Mapped port is disabled if:

No TCP/UDP service is selected
Multiple services are selected
Service group is selected
Selected service is with TCP/UDP combination

Protected zone

Select the zone to which the email server rule applies.

Specify Load balancing details.

Load balancing (only available if selected Protected server is IP range or IP list and selected Destination host/network is IP address)

Select the method for load balancing from the available options.

Available options:

Round robin: Requests are served in a sequential manner where the first request is forwarded to the first server, second request to the second server and so on. When a request is received, the device checks to see which the last server that was assigned a request was. It then assigns this new request to the next available server. This method is can be used when equal distribution of traffic is required and there is no need for session-persistence.
First alive: All incoming requests are served by the first server (the first IP address that is configured in the IP range). This server is considered as the primary server and all others are considered as backup. Only when the first server fails, the requests are forwarded to the next server in line. This method is used for failover scenarios.
Random: Requests are forwarded to the servers randomly. Although, the device makes sure that all configured servers receive equally distributed load. Hence, this is also called as uniform random distribution. This method can be used when equal distribution of traffic is required and there is no need for session-persistence or order of distribution.
Sticky IP: Along with Round Robin distribution of traffic, the device forwards incoming traffic according to the source IP address. All traffic from a particular source is forwarded only to its mapped server. This means that all requests for a given source IP are sent to the same application server instance. This method is useful in cases where all requests or sessions are required to be processed by the same server. For example: Banking websites, E-Commerce websites.

Health check (available only if Load balancing is enabled)

Click to enable health check for failover and specify the parameters based on the description shown below.

Port: Port on which the server health is monitored.
Interval: Time, in seconds, after which the health will be monitored.
Probe method: Method to use to check the health of the server.
Timeout: Time, in seconds, within which the server must respond.
Retries: Number of tries to probe the health of the server, after which the server will be declared unreachable.

Specify Identity details.

Match known users: Match known users allows you to check whether the specified user/user group from the selected zone is allowed to access the selected service or not.; Click to attach the user identity.
Show captive portal to unknown users: Select the check box to accept traffic from unknown users. Captive portal page is displayed to the user where the user can sign in to access the internet.; Clear the check box to drop traffic from unknown users.
User or groups (available only if Match known users is enabled): Select the user(s) or group(s) from the list of available options.
Exclude this user activity from data accounting (available only if Match known users is enabled): Click to enable/disable user traffic activity from data accounting.; By default, user’s network traffic is considered in data accounting. Select to exclude certain traffic from user data accounting. The traffic allowed through this firewall rule will not be accounted towards data transfer for the user.

Specify Malware scanning details.

Scan SMTP: Click to enable/disable scanning of SMTP traffic.
Scan SMTPS: Click to enable/disable scanning of SMTPS traffic.

Specify Advanced settings details.

Specify Polices for business applications.

Intrusion prevention

Select the required IPS policy. If Match rule based on user identity is enabled, user’s IPS policy will be applied automatically, but will not be effective till the respective module is subscribed.

A new IPS policy can be created directly from this page or from the Intrusion prevention > IPS policies page.

Traffic shaping policy (not available if Match known users is selected)

Select the required IPS policy. If Match rule based on user identity is enabled, user’s QoS policy will be applied automatically.

A new traffic shaping policy can be created directly from this page or from the Profiles > Traffic shaping page.
Specify Security Heartbeat settings (available only if IPv4 is selected).

Minimum source HB permitted

Select a minimum health status that a source device must have to conform to this rule. Health status can be either Green, Yellow or No restriction. If the health criterion is not met, access and privileges defined in this rule will not be granted to the user.

Block clients with no heartbeat

Heartbeat-capable devices can be required to send information on their health status in defined intervals - this is called a heartbeat.

Based on that information, you can restrict a source device’s access to certain services and networks.

Enable/disable the option to require the sending of heartbeats.

Minimum destination HB permitted (not available if Protected zone selected is WAN)

Select a minimum health status that a destination device must have to conform to this rule. Health status can be either Green, Yellow or No restriction. If the health criterion is not met, access and privileges defined in this rule will not be granted to the user.

Block request to destination with no heartbeat (not available if Protected zone selected is WAN)

Heartbeat-capable devices can be required to send information on their health status in defined intervals - this is called a heartbeat.

Based on that information, you can block requests to destinations not sending heartbeat.
Enable/disable the option to require the sending of heartbeats.
Specify Routing details.

Rewrite source address (Masquerading)

Enable/disable to re-write the source address or specify a NAT policy.

Use outbound address (available only if Rewrite source address is enabled)

Select the NAT policy to be applied from the list of available NAT policies.

A new NAT policy can be created directly from this page or from the Profiles > Network address translation page.

The default NAT policy is Masquerade.
MASQ (Interface default IP): IP address of the selected protected zone as configured in Network > Interfaces will be displayed instead of (Interface default IP).

Create reflexive rule

Select ON to automatically create a reflexive firewall rule for the protected host.

The reflexive rule has the same policies as those configured for the hosted server but instead of source zone to destination zone, this rule is applicable on traffic from destination zone to source zone.

By default, the reflexive rule is not created.

Specify the logging option for the user application traffic.

Log firewall traffic: Click to enable logging of permitted and denied traffic.