Update installation.md (#785)

* Update installation.md

Added information about endpoint customization for services not using tcp/443.

* Update installation.md

Co-authored-by: Brian969 <56414362+Brian969@users.noreply.github.com>

Author: jblaplace

docs/installation/installation.md

@@ -335,8 +335,10 @@ Issues in Older Releases:
 
 **Release Specific Upgrade Considerations:**
 
-- Upgrades to `v1.3.3 and above` from `v1.3.2 and below` requires mandatory config file schema changes as documented in the [release notes](https://github.com/aws-samples/aws-secure-environment-accelerator/releases).
-  - These updates cause the config file change validation to fail and require running the state machine with the following input to override the validation checks on impacted fields: `{"scope": "FULL", "mode": "APPLY", "configOverrides": {"ov-ou-vpc": true, "ov-ou-subnet": true, "ov-acct-vpc": true }}`
+- Upgrades to `v1.3.3 and above` from `v1.3.2 and below`:
+  - Requires mandatory config file schema changes as documented in the [release notes](https://github.com/aws-samples/aws-secure-environment-accelerator/releases).
+    - These updates cause the config file change validation to fail and require running the state machine with the following input to override the validation checks on impacted fields: `{"scope": "FULL", "mode": "APPLY", "configOverrides": {"ov-ou-vpc": true, "ov-ou-subnet": true, "ov-acct-vpc": true }}`
+    - Tightens VPC interface endpoint security group permissions and enables customization. If you use VPC interface endpoints that requires ports/protocols other than TCP/443 (such as email-smtp), you must customize your config file as described [here](/reference-artifacts/SAMPLE_CONFIGS/sample_snippets.md)
 - Upgrades to `v1.3.0 and above` from `v1.2.6 and below`:
   - **Please note MAJOR changes to state machine behavior, as documented [here](./customization-index.md#2-new-state-machine-behavior)**.
 - Upgrades to `v1.2.6 and above` from `v1.2.5 and below` - Ensure you apply the config file changes described in the release notes: