diff --git a/app/modules/domain_management/services.py b/app/modules/domain_management/services.py
index 9a89f62..4f504e4 100644
--- a/app/modules/domain_management/services.py
+++ b/app/modules/domain_management/services.py
@@ -4,7 +4,6 @@ import re
 import secrets
 import socket
 import ssl
-import subprocess
 from dataclasses import dataclass
 from datetime import datetime, timezone
 from email.utils import parsedate_to_datetime
@@ -598,64 +597,53 @@ def _normalise_txt_value(value: str) -> str:
 
 
 def _resolve_txt_with_dnspython(txt_name: str) -> tuple[list[str], str | None]:
+    """Resolve TXT records using the Python DNS resolver.
+
+    Production containers should not depend on OS tools such as nslookup/dig.
+    The package dependency is declared in requirements.txt as dnspython.
+    """
     try:
+        import dns.exception  # type: ignore
         import dns.resolver  # type: ignore
-    except Exception:
-        return [], "dnspython is not installed"
-    try:
-        answers = dns.resolver.resolve(txt_name, "TXT")
-        values: list[str] = []
-        for answer in answers:
-            try:
-                chunks = [part.decode("utf-8", errors="ignore") if isinstance(part, bytes) else str(part) for part in answer.strings]
-                values.append("".join(chunks))
-            except Exception:
-                values.append(str(answer).strip())
-        return values, None
     except Exception as exc:
-        return [], str(exc)
+        return [], f"dnspython package is not installed or not importable: {exc}"
 
+    resolver = dns.resolver.Resolver(configure=True)
+    resolver.lifetime = 12.0
+    resolver.timeout = 4.0
 
-def _resolve_txt_with_nslookup(txt_name: str) -> tuple[list[str], str | None]:
     try:
-        completed = subprocess.run(
-            ["nslookup", "-type=TXT", txt_name],
-            capture_output=True,
-            text=True,
-            timeout=12,
-            check=False,
-        )
-    except FileNotFoundError:
-        return [], "nslookup command is not available on this machine"
+        answers = resolver.resolve(txt_name, "TXT")
+    except dns.resolver.NXDOMAIN:
+        return [], f"TXT name does not exist: {txt_name}"
+    except dns.resolver.NoAnswer:
+        return [], f"No TXT records found for: {txt_name}"
+    except dns.resolver.NoNameservers as exc:
+        return [], f"DNS nameserver failed for {txt_name}: {exc}"
+    except dns.exception.Timeout:
+        return [], f"DNS lookup timed out for: {txt_name}"
     except Exception as exc:
-        return [], str(exc)
-
-    output = "\n".join([completed.stdout or "", completed.stderr or ""])
-    if completed.returncode != 0 and not output.strip():
-        return [], "DNS lookup failed"
+        return [], f"DNS lookup failed for {txt_name}: {exc}"
 
     values: list[str] = []
-    for line in output.splitlines():
-        line = line.strip()
-        if not line:
-            continue
-        # Windows/Linux nslookup generally prints TXT values inside quotes.
-        quoted = re.findall(r'"([^"]+)"', line)
-        if quoted:
-            values.append("".join(quoted))
-            continue
-        if "text =" in line.lower():
-            values.append(line.split("=", 1)[1].strip())
-    if not values and output.strip():
-        # Keep a short diagnostic without storing full command noise.
-        return [], output.strip().splitlines()[-1][:240]
+    for answer in answers:
+        try:
+            # dnspython TXT records may be split into multiple byte chunks.
+            chunks = [
+                part.decode("utf-8", errors="ignore") if isinstance(part, bytes) else str(part)
+                for part in getattr(answer, "strings", [])
+            ]
+            values.append("".join(chunks) if chunks else answer.to_text().strip())
+        except Exception:
+            values.append(str(answer).strip())
     return values, None
 
 
 def lookup_dns_txt_values(txt_name: str) -> tuple[list[str], str | None]:
-    """Return TXT records for a DNS name using dnspython when available, else nslookup.
+    """Return TXT records for a DNS name using dnspython only.
 
-    No new dependency is required. On Windows, nslookup is normally available by default.
+    This avoids failures in minimal Docker/Coolify containers where the nslookup
+    command is not installed. Install dependencies with `pip install -r requirements.txt`.
     """
     txt_name = normalize_domain(txt_name)
     if not txt_name:
@@ -664,12 +652,7 @@ def lookup_dns_txt_values(txt_name: str) -> tuple[list[str], str | None]:
     values, error = _resolve_txt_with_dnspython(txt_name)
     if values:
         return [_normalise_txt_value(v) for v in values], None
-
-    ns_values, ns_error = _resolve_txt_with_nslookup(txt_name)
-    if ns_values:
-        return [_normalise_txt_value(v) for v in ns_values], None
-
-    return [], ns_error or error or "No TXT record found"
+    return [], error or "No TXT record found"
 
 
 def verify_domain_dns_txt(db: Session, mapping: DomainMapping, *, user_id: int | None) -> DomainDnsVerificationResult:
diff --git a/requirements.txt b/requirements.txt
index e82f580..bd3c841 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -12,6 +12,6 @@ alembic==1.14.0
 psycopg[binary]==3.2.3
 pydantic[email]
 email-validator
+dnspython==2.7.0
 openpyxl
-dnspython
 itsdangerous