diff --git a/app/models/better_together/platform_invitation.rb b/app/models/better_together/platform_invitation.rb
index 286bef8fd..f70c2f4ba 100644
--- a/app/models/better_together/platform_invitation.rb
+++ b/app/models/better_together/platform_invitation.rb
@@ -32,8 +32,10 @@ class PlatformInvitation < ApplicationRecord
 
     has_rich_text :greeting, encrypted: true
 
-    validates :invitee_email, uniqueness: { scope: :invitable_id, allow_nil: true }
-    validates :invitee_email, uniqueness: { scope: :invitable_id, allow_nil: true, allow_blank: true }
+    validates :invitee_email,
+              uniqueness: { scope: :invitable_id, case_sensitive: false },
+              format: { with: URI::MailTo::EMAIL_REGEXP },
+              allow_blank: true
     validates :locale, presence: true, inclusion: { in: I18n.available_locales.map(&:to_s) }
     validates :status, presence: true, inclusion: { in: STATUS_VALUES.values }
     validates :token, uniqueness: true
@@ -46,8 +48,9 @@ class PlatformInvitation < ApplicationRecord
 
     scope :pending, -> { where(status: STATUS_VALUES[:pending]) }
     scope :accepted, -> { where(status: STATUS_VALUES[:accepted]) }
-    scope :expired, -> { where('valid_until IS NOT NULL AND valid_until < ?', Time.current) }
-    scope :not_expired, -> { where('valid_until IS NULL OR valid_until >= ?', Time.current) }
+
+    scope :expired, -> { where('valid_until IS NULL OR valid_until < ?', Time.current) }
+    scope :not_expired, -> { where('valid_until >= ?', Time.current) }
 
     def self.load_all_subclasses
       Rails.application.eager_load! # Ensure all models are loaded
diff --git a/spec/models/better_together/platform_invitation_spec.rb b/spec/models/better_together/platform_invitation_spec.rb
index d093a1101..05e1d6a17 100644
--- a/spec/models/better_together/platform_invitation_spec.rb
+++ b/spec/models/better_together/platform_invitation_spec.rb
@@ -24,12 +24,11 @@ module BetterTogether # rubocop:todo Metrics/ModuleLength
 
     describe 'ActiveModel validations' do
       it {
-        # rubocop:todo RSpec/NamedSubject
-        expect(subject).to validate_uniqueness_of(:invitee_email).scoped_to(:invitable_id)
-                                                                 # rubocop:enable RSpec/NamedSubject
-                                                                 .allow_nil.allow_blank.case_insensitive
+        is_expected.to validate_uniqueness_of(:invitee_email).scoped_to(:invitable_id)
+                                                             .allow_blank.case_insensitive
       }
-
+      it { is_expected.to allow_value('test@example.com').for(:invitee_email) }
+      it { is_expected.not_to allow_value('invalid_email').for(:invitee_email) }
       it { is_expected.to validate_presence_of(:locale) }
       it { is_expected.to validate_inclusion_of(:locale).in_array(I18n.available_locales.map(&:to_s)) }
       it { is_expected.to validate_presence_of(:status) }
@@ -89,27 +88,22 @@ module BetterTogether # rubocop:todo Metrics/ModuleLength
       end
 
       describe '.expired' do
-        it 'returns only expired invitations' do # rubocop:todo RSpec/MultipleExpectations
-          expired_invitation = create(:better_together_platform_invitation, valid_until: 1.day.ago)
+        it 'includes invitations with nil or past valid_until' do
+          nil_invitation = create(:better_together_platform_invitation, valid_until: nil)
+          past_invitation = create(:better_together_platform_invitation, valid_until: 1.day.ago)
           create(:better_together_platform_invitation, valid_until: 1.day.from_now)
 
-          expect(described_class.expired).to include(expired_invitation)
-          expect(described_class.expired.count).to eq(1)
+          expect(described_class.expired).to match_array([nil_invitation, past_invitation])
         end
       end
 
       describe '.not_expired' do
-        # rubocop:todo RSpec/MultipleExpectations
-        it 'returns invitations that are not expired or have no expiration' do # rubocop:todo RSpec/ExampleLength, RSpec/MultipleExpectations
-          # rubocop:enable RSpec/MultipleExpectations
-          future_invitation = create(:better_together_platform_invitation, valid_until: 1.day.from_now)
-          nil_invitation = create(:better_together_platform_invitation, valid_until: nil)
+        it 'includes only invitations with future valid_until' do
+          create(:better_together_platform_invitation, valid_until: nil)
           create(:better_together_platform_invitation, valid_until: 1.day.ago)
+          future_invitation = create(:better_together_platform_invitation, valid_until: 1.day.from_now)
 
-          result = described_class.not_expired
-
-          expect(result).to include(future_invitation, nil_invitation)
-          expect(result.count).to eq(2)
+          expect(described_class.not_expired).to match_array([future_invitation])
         end
       end
     end