diff --git a/dnsapi/dns_udr.sh b/dnsapi/dns_udr.sh
new file mode 100644
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+++ b/dnsapi/dns_udr.sh
@@ -0,0 +1,160 @@
+#!/usr/bin/env sh
+
+# united-domains Reselling (https://www.ud-reselling.com/) DNS API
+# Author: Andreas Scherer (https://github.com/andischerer)
+# Created: 2021-02-01
+#
+# Set the environment variables as below:
+#
+#    export UDR_USER="your_username_goes_here"
+#    export UDR_PASS="some_password_goes_here"
+#
+
+UDR_API="https://api.domainreselling.de/api/call.cgi"
+UDR_TTL="30"
+
+########  Public functions #####################
+
+#Usage: add _acme-challenge.www.domain.com "some_long_string_of_characters_go_here_from_lets_encrypt"
+dns_udr_add() {
+  fulldomain=$1
+  txtvalue=$2
+
+  UDR_USER="${UDR_USER:-$(_readaccountconf_mutable UDR_USER)}"
+  UDR_PASS="${UDR_PASS:-$(_readaccountconf_mutable UDR_PASS)}"
+  if [ -z "$UDR_USER" ] || [ -z "$UDR_PASS" ]; then
+    UDR_USER=""
+    UDR_PASS=""
+    _err "You didn't specify an UD-Reselling username and password yet"
+    return 1
+  fi
+  # save the username and password to the account conf file.
+  _saveaccountconf_mutable UDR_USER "$UDR_USER"
+  _saveaccountconf_mutable UDR_PASS "$UDR_PASS"
+  _debug "First detect the root zone"
+  if ! _get_root "$fulldomain"; then
+    _err "invalid domain"
+    return 1
+  fi
+
+  _debug _dnszone "${_dnszone}"
+
+  _debug "Getting txt records"
+  if ! _udr_rest "QueryDNSZoneRRList" "dnszone=${_dnszone}"; then
+    return 1
+  fi
+
+  rr="${fulldomain}. ${UDR_TTL} IN TXT ${txtvalue}"
+  _debug resource_record "${rr}"
+  if _contains "$response" "$rr" >/dev/null; then
+    _err "Error, it would appear that this record already exists. Please review existing TXT records for this domain."
+    return 1
+  fi
+
+  _info "Adding record"
+  if ! _udr_rest "UpdateDNSZone" "dnszone=${_dnszone}&addrr0=${rr}"; then
+    _err "Adding the record did not succeed, please verify/check."
+    return 1
+  fi
+
+  _info "Added, OK"
+  return 0
+}
+
+dns_udr_rm() {
+  fulldomain=$1
+  txtvalue=$2
+
+  UDR_USER="${UDR_USER:-$(_readaccountconf_mutable UDR_USER)}"
+  UDR_PASS="${UDR_PASS:-$(_readaccountconf_mutable UDR_PASS)}"
+  if [ -z "$UDR_USER" ] || [ -z "$UDR_PASS" ]; then
+    UDR_USER=""
+    UDR_PASS=""
+    _err "You didn't specify an UD-Reselling username and password yet"
+    return 1
+  fi
+
+  _debug "First detect the root zone"
+  if ! _get_root "$fulldomain"; then
+    _err "invalid domain"
+    return 1
+  fi
+  _debug _dnszone "${_dnszone}"
+
+  _debug "Getting txt records"
+  if ! _udr_rest "QueryDNSZoneRRList" "dnszone=${_dnszone}"; then
+    return 1
+  fi
+
+  rr="${fulldomain}. ${UDR_TTL} IN TXT ${txtvalue}"
+  _debug resource_record "${rr}"
+  if _contains "$response" "$rr" >/dev/null; then
+    if ! _udr_rest "UpdateDNSZone" "dnszone=${_dnszone}&delrr0=${rr}"; then
+      _err "Deleting the record did not succeed, please verify/check."
+      return 1
+    fi
+    _info "Removed, OK"
+    return 0
+  else
+    _info "Text record is not present, will not delete anything."
+    return 0
+  fi
+}
+
+####################  Private functions below ##################################
+#_acme-challenge.www.domain.com
+#returns
+# _sub_domain=_acme-challenge.www
+# _domain=domain.com
+_get_root() {
+  domain=$1
+  i=1
+
+  if ! _udr_rest "QueryDNSZoneList" ""; then
+    return 1
+  fi
+
+  while true; do
+    h=$(printf "%s" "$domain" | cut -d . -f $i-100)
+    _debug h "$h"
+
+    if [ -z "$h" ]; then
+      #not valid
+      return 1
+    fi
+
+    if _contains "${response}" "${h}." >/dev/null; then
+      _dnszone=$(echo "$response" | _egrep_o "${h}")
+      if [ "$_dnszone" ]; then
+        return 0
+      fi
+      return 1
+    fi
+    i=$(_math "$i" + 1)
+  done
+  return 1
+}
+
+_udr_rest() {
+  if [ -n "$2" ]; then
+    data="command=$1&$2"
+  else
+    data="command=$1"
+  fi
+
+  _debug data "${data}"
+  response="$(_post "${data}" "${UDR_API}?s_login=${UDR_USER}&s_pw=${UDR_PASS}" "" "POST")"
+
+  _code=$(echo "$response" | _egrep_o "code = ([0-9]+)" | _head_n 1 | cut -d = -f 2 | sed -e 's/^[[:space:]]*//' -e 's/[[:space:]]*$//')
+  _description=$(echo "$response" | _egrep_o "description = .*" | _head_n 1 | cut -d = -f 2 | sed -e 's/^[[:space:]]*//' -e 's/[[:space:]]*$//')
+
+  _debug response_code "$_code"
+  _debug response_description "$_description"
+
+  if [ ! "$_code" = "200" ]; then
+    _err "DNS-API-Error: $_description"
+    return 1
+  fi
+
+  return 0
+}