Smtp load balancing
Kemp technologies load balancer
Setting up load-balancing with port 25 is a common nightmare for Microsoft Exchange Server administrators. They have the problem that they no longer see the originating client IPs of the individual clients in these setups; all traffic is converted and addressed to the SMTP service with the load balancer IP as the source. Working with receive connectors becomes extremely complicated as a result of this. For the SMTP service, several organisations have chosen to use multiple virtual IPs and/or different port numbers…
I believe there is a better way. The Direct Server Return option on load balancers, in my opinion, is a better solution; this option allows the load balancer to present the original client IP to the back-end server, in our case, Microsoft Exchange Server’s SMTP service. Instead of using a load balancer, the back-end server sends response packets directly to the client (no Server Network Address Translation (NAT)).
This works perfectly if the client, the load balancer, and the back-end server are all on the same subnet or if there are no firewalls between the client, the load balancer, and the back-end server. If a firewall is involved in the communications flow, the firewall will drop connections due to asymmetric traffic flows; the firewall finds that the TCP information may not match what it already knows.
Outgoing mail server load balancing
SMTPS and SMTP-STARTLS can be SSL-offloaded to SMTP using the LoadMaster, but SMTP-STARTLS cannot be re-encrypted.
Incoming mail server load balancing
If you want to load balance SMTP-STARTLS, either adjust the Real Server to accept SMTP or set the service form to Generic.
Options for virtual service routing are shown in Figure 6. If you have Transparency turned on, this is the client’s IP address. This is the IP address of the individual active LoadMaster interface if Subnet Originating Requests is allowed. This is the IP address of the Virtual Service if Transparency and Subnet Originating Requests are disabled. Enable transparency on the LoadMaster if you want the Exchange server to allow or reject client access to the receive connector based on the client’s IP address. Refer to the Transparency Function Overview for more details.
If clarity isn’t an option, Access Control Lists (ACLs) on the LoadMaster can be used to grant or deny a client access to the receive connector.
Refer to this article for more information: Building an Access Control List (ACL).
Devops & sysadmins: load balancing of recipients email
We’ll set up a simple TCP load balancing service for one or more SMTP servers in this guide. On port 25, a TCP front-end can listen for TCP traffic. Depending on how you configure it, it is configured to send traffic to a TCP farm with one or more TCP servers.
Pick the farm to which you want to connect a server by clicking on the corresponding line in the Farms tab. The list of servers already configured in the farm, as well as the Add a server button, will appear underneath the list of farms. To add a new server, press this button.
The IPv4 address, Status, and ProxyProtocol version fields are the only ones that must be filled in. By configuring a server, you can overload it if it does not use the same port as the one specified earlier in the farm. However, we suggest only using this parameter in advanced cases to keep the configuration as standard as possible and easy to manage.
Complete the fields. Only Port (25 for a standard SMTP service), Zone, and Probe (if your farm has one) are required fields for a simple configuration. You may define a list of ports separated by commas or a number of ports in the format “start port-end port” if you want your service to be available on multiple ports at the same time.
Load balancer 101 for microsoft exchange 2010 / 2013 / 2016
If your company has multiple Exchange Servers, you’ll want to load balance Exchange SMTP for high availability. Kemp is a fantastic load balancer that we suggest. This article will show you how to use Kemp load balancer to load balance Exchange SMTP for high availability.
Both HTTPS and SMTP are network layer protocols for sharing data between hosts. HTTPS is used to transmit encrypted communication over a network, while SMTP is used to transfer emails between mail servers.
Check to see if the IP address was taken by another user. If you’re replacing an old load balancer with Kemp LoadMaster, you can retain the same IP address. Kemp LoadMaster can handle the SMTP mail switch.
It’s always a good idea to test the load balancer to see if it’s working properly. Check the statistics after disabling the network card on one of the Exchange Servers. The Exchange Server status will be reflected in real time statistics.
You learned how to set up Exchange SMTP high availability with Kemp load balancer in this post. Kemp offers some excellent templates. To load balance Exchange inbound SMTP with Kemp LoadMaster, follow the steps below. Finally, use Microsoft Remote Communication Analyzer (MRCA) to test the SMTP flow, or send an email and check the headers.