Doc: ha_proxy_client fix for changed remote IP (TASK-227757)

content/momentum/4/modules/ha-proxy-client.md

@@ -1,12 +1,13 @@
 ---
-lastUpdated: "10/05/2021"
+lastUpdated: "05/20/2026"
 title: "ha_proxy_client - HAProxy protocol client module"
 description: "The ha_proxy_client module is used to configure Momentum to use HAProxy's PROXY protocol version 2 for outbound connections (see https://github.com/haproxy/haproxy/blob/master/doc/proxy-protocol.txt).  This can be leveraged in cases where your sending IPs are deployed on a different machine than Momentum."
 ---
 
 ## Configuration
 
 * When configured for a binding or binding group Momentum will connect to the given `ha_proxy_server` and prefix the SMTP session with a PROXY protocol version 2 header.  
+* `ha_proxy_server` accepts either a literal `IP:port` or a `hostname:port`.  When a hostname is used, Momentum resolves it at configuration load and then re-checks DNS during each [health check](#health-check): if the resolved address leaves the answer set (for example, the backend was redeployed with a new IP) Momentum will switch new connections to the updated address automatically, with no restart or configuration reload required.  Detection happens through Momentum's DNS cache, so the [`resolv_conf`](/momentum/4/config/ref-resolv-conf) setting and DNS TTLs apply; expect a delay of up to one health check interval plus the record TTL before the switch.
 * The `dst_addr` and `dst_port` will be filled in with the resolved MX, the `src_addr` will be filled in with the configured value of `ha_proxy_src_addr` if the destination family is IPV4, or `ha_proxy_ipv6_src_addr` if the destination family is IPV6.  If you need to deliver to both IPV4 and IPV6 destinations then you must configure both options for the binding or binding_group.  
 * The `ha_proxy_bypass` option allows you to bypass the proxy and follow the normal delivery method on a domain by domain basis.
 * It is the customers responsibility to configure a listener at `ha_proxy_server` that   listens for PROXY protocol and forwards traffic based on `dst_addr:dst_port`. 

content/momentum/changelog/5/5-3-0.md

@@ -12,3 +12,4 @@ This section will list all of the major changes that happened with the release o
 | --- | --- | --- |
 | Feature | I-1064 | Added support for [license](/momentum/4/before-you-begin#momentum-license) signatures using ECDSA P-256 with SHA-256. |
 | Feature | I-1214 | Removed `msys-nodejs` RPM from the Momentum bundle, to be replaced with the 3rd-party `nodejs` package. Node.js LTS 24+ must be installed separately from the system or a vendor repository. |
+| Fix | TASK-227757 | [`ha_proxy_client`](/momentum/4/modules/ha-proxy-client) now re-resolves a hostname-based `ha_proxy_server` during each health check, so backend IP changes are picked up automatically without restart. |