diff --git a/app/controllers/invitations_controller.rb b/app/controllers/invitations_controller.rb
index b3be607c..8db5cfa5 100644
--- a/app/controllers/invitations_controller.rb
+++ b/app/controllers/invitations_controller.rb
@@ -47,10 +47,11 @@ class InvitationsController < ApplicationController
     body = invitation_params[:body]
 
     invitation_token = SecureRandom.hex(16)
+    invitation = Invitation.new(email: to, token_digest: Digest::SHA256.hexdigest(invitation_token))
     subject = "[TEST] " + subject
     body_with_link = body.gsub('%link%', get_url_for(method(:new_user_registration_url), options: { invitation_token: invitation_token, email: to }))
 
-    InvitationMailer.invite(to: to, subject: subject, body: body_with_link).deliver_later
+    InvitationMailer.invite(invitation: invitation, subject: subject, body: body_with_link).deliver_now
 
     render json: {}, status: :ok
   end
diff --git a/app/views/invitation_mailer/invite.html.erb b/app/views/invitation_mailer/invite.html.erb
index 2f21cf84..75ba9df9 100644
--- a/app/views/invitation_mailer/invite.html.erb
+++ b/app/views/invitation_mailer/invite.html.erb
@@ -1 +1 @@
-<%= @body %>
\ No newline at end of file
+<%= simple_format(@body) %>
\ No newline at end of file
diff --git a/app/workflows/o_auth_sign_in_user_workflow.rb b/app/workflows/o_auth_sign_in_user_workflow.rb
index 9e09a9de..fba537f5 100644
--- a/app/workflows/o_auth_sign_in_user_workflow.rb
+++ b/app/workflows/o_auth_sign_in_user_workflow.rb
@@ -40,15 +40,24 @@ class OAuthSignInUserWorkflow
         end
         full_name ||= I18n.t('defaults.user_full_name')
 
-        user = User.new(
-          email: email,
-          full_name: full_name,
-          password: Devise.friendly_token,
-          has_set_password: false,
-          status: 'active'
-        )
-        user.skip_confirmation
-        user.save
+        ActiveRecord::Base.transaction do
+          user = User.new(
+            email: email,
+            full_name: full_name,
+            password: Devise.friendly_token,
+            has_set_password: false,
+            status: 'active'
+          )
+          user.skip_confirmation
+          user.save
+          
+          # if there is a pending invitation for this email, mark it as accepted
+          invitation = Invitation.find_by(email: email)
+          if invitation && invitation.accepted_at.nil?
+            invitation.accepted_at = Time.now
+            invitation.save!
+          end
+        end
       end
 
       return user