Manually opening Ports to allow Email traffic (SMTP, IMAP or POP3) from Internet to a server behind the SonicWALL in SonicOS Enhanced involves the following steps:
Step 1: Creating the necessary Address Objects
Step 2: Create a Service Group
Step 2: Defining the appropriate NAT Policies (Inbound, Outbound and Loopback)
Step 3: Creating the necessary WAN > Zone Access Rules for public access
Recommendation: The Public Server Wizard quickly configure your SonicWALL to provide public access to an internal server. The Public Server Wizard is the most ambitious and functional wizard developed to date. It simplifies the complex process of creating a publicly and internally accessible server resource by automating above mentioned steps.Scenario:
The following example covers allowing Email traffic (SMTP, IMAP or POP3) service from the Internet to a server on the LAN with private IP address as 192.168.1.100. Once the configuration is complete, Internet users can Send emails to the Email Server behind the SonicWALL UTM appliance through the WAN (Public) IP address 1.1.1.1.
Procedure:
In this example we have chosen to demonstrate using SMTP service, however the following steps apply to any service you wish to use (like HTTPS, SMTP, FTP, Terminal Services, SSH, etc).
Step 1: Creating the necessary Address Objects
1. Select Network > Address Objects.
2. Click the Add a new address object button and create two address objects one for Server IP on LAN and another for Public IP of the server:
Address Object for Server on LAN
Name: MailServer Private
Zone Assignment: LAN
Type: Host
IP Address: 192.168.1.100
Address Object for Server's Public IP
Name: MailServer Public
Zone Assignment: WAN
Type: Host
IP Address: 1.1.1.1
3.Click the OK button to complete creation of the new address objects.
Step 2: Create a Service Group
1. The Services page can be accessed either from Firewall > Services or Network > Services.
2. Click Add Group.
3.Select individual services from the list in the left column. Click - > to add the services to the group.
4.To remove services from the group, select individual services from the list in right column. Click < -to remove the services.
5.When you are finished, click OK to add the group to Custom Services Groups.
Step 3: Defining the appropriateNAT Policies
1. Select Network > NAT Policies.
2. Click the Add a new NAT Policy button and chose the following settings from the drop-down menu:
Understanding how to use NAT policies starts with the construction of an IP packet. Every packet contains addressing information that allows the packet to get to its destination, and for the destination to respond to the original requester. The packet contains (among other things) the requester’s IP address, the protocol information of the requestor, and the destination’s IP address. The NAT Policies engine in SonicOS Enhanced can inspect the relevant portions of the packet and can dynamically rewrite the information in specified fields for incoming, as well as outgoing traffic.
Adding appropriate NAT Policies
Original Source: Any
Translated Source: Original
Original Destination: MailServer Public
Translated Destination: MailServer Private
Original Service: MailServer Services
Translated Service: Original
Inbound Interface: Any
Outbound Interface: Any
Comment: Webserver behind SonicWALL.
Enable NAT Policy: Checked
Create a reflexive policy: Checked
Note: Create a reflective policy: When you check this box, a mirror outbound or inbound NAT policy for the NAT policy you defined in the Add NAT Policy window is automatically created.
3. Click the Addbutton.
Loopback Policy:
If you wish to access this server from other internal zones using the Public IP address 1.1.1.1 consider creating a Loopback NAT Policy else go to next step:
Original Source: Firewalled Subnets
Translated Source: MailServer Public
Original Destination: MailServer Public
Translated Destination: MailServer Private
Original Service: MailServer Services
Translated Service: Original
Inbound Interface: Any
Outbound Interface: Any
Comment: Loopback policy
Enable NAT Policy: Checked
Create a reflexive policy: unchecked
4. Upon completion under Network > Nat Policies tab the above Inboundand Outbond NAT policies will be created.
Step 3: Creating Firewall Access Rules
1. Click Firewall > Access Rules tab.
2. Select the type of view in the View Style section and go to WAN to LAN access rules.
3.Click Add a new entry and create the rule by entering the following into the fields:
Caution: The ability to define network access rules is a very powerful tool. Using custom access rules can disable firewall protection or block all access to the Internet. Use caution when creating or deleting network access rules.
Action: Allow
From Zone: WAN
To Zone: LAN
Service: MailServer Services
Source: Any
Destination: MailServer Public
Users Allowed: All
Schedule: Always on
Enable Logging: checked
Allow Fragmented Packets: checked
5:Click OK.
How to Test:
Testing from within the private network: Ensure that the Email Server is working from within the private network itself.
Testing from the Internet: Go to www.mxtoolbox.com and enter your Email Server's Public IP address in the Domain Name field i.e 1.1.1.1
Troubleshooting:
Ensure that the EmailServer's Default Gateway IP address is SonicWALL's LAN IP address.
Ensure that the Email Server is able to access the Internet.
Try to reduce the MTU value on your SonicWALL appliance.
Displaying Access Rule Traffic Statistics:
1. Click Firewall > Access Rules tab.
2. Select the type of view in the View Style section and go to WAN to LAN access rules.
3.Move your mouse pointer over the Graph icon to display the following access rule receive (Rx) and transmit (Tx) traffic statistics:
• Rx Bytes
• Rx Packets
• Tx Bytes
• Tx Packets
Ensure you do not have duplicate NAT Policies and Firewall Access Rules for your Email Server.
For further troubleshooting go to SonicWALL Logs under Log > View page and check for Alerts, Denied IP's, Dropped messages, etc.
