diff --git a/lib/diaspora_federation/validators/rules/diaspora_id.rb b/lib/diaspora_federation/validators/rules/diaspora_id.rb
index 8b94a7e..a57ee47 100644
--- a/lib/diaspora_federation/validators/rules/diaspora_id.rb
+++ b/lib/diaspora_federation/validators/rules/diaspora_id.rb
@@ -2,23 +2,20 @@ module Validation
   module Rule
     # Diaspora ID validation rule
     #
-    # This rule is based on https://github.com/zombor/Validator/blob/master/lib/validation/rule/email.rb
-    # which was adapted from https://github.com/emmanuel/aequitas/blob/master/lib/aequitas/rule/format/email_address.rb
+    # A simple rule to validate the base structure of diaspora IDs.
     class DiasporaId
       # The Regex for a valid diaspora ID
       DIASPORA_ID = begin
         letter         = "a-zA-Z"
         digit          = "0-9"
+        hexadecimal    = "[a-fA-F#{digit}]"
         username       = "[#{letter}#{digit}\\-\\_\\.]+"
-        atext          = "[#{letter}#{digit}+\\=\\-\\_]"
-        dot_atom       = "#{atext}+([.]#{atext}*)*"
-        no_ws_ctl      = '\x01-\x08\x11\x12\x14-\x1f\x7f'
-        text           = '[\x01-\x09\x11\x12\x14-\x7f]'
-        quoted_pair    = "(\\x5c#{text})"
-        dtext          = "[#{no_ws_ctl}\\x21-\\x5a\\x5e-\\x7e]"
-        dcontent       = "(?:#{dtext}|#{quoted_pair})"
-        domain_literal = "\\[#{dcontent}+\\]"
-        domain         = "(?:#{dot_atom}|#{domain_literal})"
+        hostname_part  = "[#{letter}#{digit}\\-]"
+        hostname       = "#{hostname_part}+([.]#{hostname_part}*)*"
+        ipv4           = "(?:[#{digit}]{1,3}\\.){3}[#{digit}]{1,3}"
+        ipv6           = "\\[(?:#{hexadecimal}{0,4}:){0,7}#{hexadecimal}{1,4}\\]"
+        ip_addr        = "(?:#{ipv4}|#{ipv6})"
+        domain         = "(?:#{hostname}|#{ip_addr})"
         port           = "(:[#{digit}]+)?"
         addr_spec      = "(#{username}\\@#{domain}#{port})?"
 
diff --git a/lib/diaspora_federation/validators/rules/diaspora_id_count.rb b/lib/diaspora_federation/validators/rules/diaspora_id_count.rb
index fac7d99..35fa189 100644
--- a/lib/diaspora_federation/validators/rules/diaspora_id_count.rb
+++ b/lib/diaspora_federation/validators/rules/diaspora_id_count.rb
@@ -28,7 +28,7 @@ module Validation
         ids = value.split(";")
         return false unless ids.count <= params[:maximum]
         ids.each do |id|
-          return false unless DiasporaId.new.valid_value?(id)
+          return false if DiasporaId::DIASPORA_ID.match(id).nil?
         end
         true
       end
diff --git a/spec/lib/diaspora_federation/validators/rules/diaspora_id_spec.rb b/spec/lib/diaspora_federation/validators/rules/diaspora_id_spec.rb
index 889d6d9..b87fabe 100644
--- a/spec/lib/diaspora_federation/validators/rules/diaspora_id_spec.rb
+++ b/spec/lib/diaspora_federation/validators/rules/diaspora_id_spec.rb
@@ -67,6 +67,14 @@ describe Validation::Rule::DiasporaId do
       expect(validator.errors).to include(:diaspora_id)
     end
 
+    it "fails if the diaspora id contains a _ in the domain-name" do
+      validator = Validation::Validator.new(OpenStruct.new(diaspora_id: "some_user@invalid_domain.com"))
+      validator.rule(:diaspora_id, :diaspora_id)
+
+      expect(validator).not_to be_valid
+      expect(validator.errors).to include(:diaspora_id)
+    end
+
     it "fails if the diaspora id contains a special-chars in the username" do
       validator = Validation::Validator.new(OpenStruct.new(diaspora_id: "some_user$^%@example.com"))
       validator.rule(:diaspora_id, :diaspora_id)