diff --git a/CHANGELOG.md b/CHANGELOG.md
index 753c69e..59bd5d3 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,13 @@
 Changelog
 =========
 
+8.18.3
+------
+
+- Move `__version__` to `parsedmarc.constants`
+- Create a constant `USER_AGENT`
+- Use the HTTP `User-Agent` header value `parsedmarc/version` for all HTTP requests
+
 8.18.2
 ------
 
diff --git a/parsedmarc/__init__.py b/parsedmarc/__init__.py
index faa1f56..2169136 100644
--- a/parsedmarc/__init__.py
+++ b/parsedmarc/__init__.py
@@ -34,12 +34,13 @@ from parsedmarc.mail import (
     MSGraphConnection,
     GmailConnection,
 )
+
+from parsedmarc.constants import __version__
 from parsedmarc.utils import get_base_domain, get_ip_address_info
 from parsedmarc.utils import is_outlook_msg, convert_outlook_msg
 from parsedmarc.utils import parse_email
 from parsedmarc.utils import timestamp_to_human, human_timestamp_to_datetime
 
-__version__ = "8.18.2"
 
 logger.debug("parsedmarc v{0}".format(__version__))
 
diff --git a/parsedmarc/constants.py b/parsedmarc/constants.py
new file mode 100644
index 0000000..80e0a50
--- /dev/null
+++ b/parsedmarc/constants.py
@@ -0,0 +1,2 @@
+__version__ = "8.18.3"
+USER_AGENT = f"parsedmarc/{__version__}"
diff --git a/parsedmarc/splunk.py b/parsedmarc/splunk.py
index cf6a1e0..3e218fb 100644
--- a/parsedmarc/splunk.py
+++ b/parsedmarc/splunk.py
@@ -5,7 +5,7 @@ import json
 import urllib3
 import requests
 
-from parsedmarc import __version__
+from parsedmarc.constants import USER_AGENT
 from parsedmarc.log import logger
 from parsedmarc.utils import human_timestamp_to_unix_timestamp
 
@@ -51,7 +51,7 @@ class HECClient(object):
         self._common_data = dict(host=self.host, source=self.source, index=self.index)
 
         self.session.headers = {
-            "User-Agent": "parsedmarc/{0}".format(__version__),
+            "User-Agent": USER_AGENT,
             "Authorization": "Splunk {0}".format(self.access_token),
         }
 
diff --git a/parsedmarc/utils.py b/parsedmarc/utils.py
index 60c7071..571cca5 100644
--- a/parsedmarc/utils.py
+++ b/parsedmarc/utils.py
@@ -37,7 +37,7 @@ import requests
 from parsedmarc.log import logger
 import parsedmarc.resources.dbip
 import parsedmarc.resources.maps
-
+from parsedmarc.constants import USER_AGENT
 
 parenthesis_regex = re.compile(r"\s*\(.*\)\s*")
 
@@ -345,7 +345,8 @@ def get_service_from_reverse_dns_base_domain(
     if not (offline or always_use_local_file) and len(reverse_dns_map) == 0:
         try:
             logger.debug(f"Trying to fetch reverse DNS map from {url}...")
-            response = requests.get(url)
+            headers = {"User-Agent", USER_AGENT}
+            response = requests.get(url, headers=headers)
             response.raise_for_status()
             csv_file.write(response.text)
             csv_file.seek(0)
diff --git a/parsedmarc/webhook.py b/parsedmarc/webhook.py
index b54ab65..37477e6 100644
--- a/parsedmarc/webhook.py
+++ b/parsedmarc/webhook.py
@@ -1,6 +1,6 @@
 import requests
 
-from parsedmarc import logger
+from parsedmarc import logger, USER_AGENT
 
 
 class WebhookClient(object):
@@ -21,7 +21,7 @@ class WebhookClient(object):
         self.timeout = timeout
         self.session = requests.Session()
         self.session.headers = {
-            "User-Agent": "parsedmarc",
+            "User-Agent": USER_AGENT,
             "Content-Type": "application/json",
         }
 
diff --git a/pyproject.toml b/pyproject.toml
index fc7e537..6f84e9a 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -76,7 +76,7 @@ parsedmarc = "parsedmarc.cli:_main"
 Homepage = "https://domainaware.github.io/parsedmarc"
 
 [tool.hatch.version]
-path = "parsedmarc/__init__.py"
+path = "parsedmarc/constants.py"
 
 [tool.hatch.build.targets.sdist]
 include = [