FIX: add site setting email_site_title, which overrides title in reply by email address in case the title has invalid characters

config/locales/server.en.yml

@@ -881,6 +881,7 @@ en:
     email_in_min_trust: "The minimum trust level an users needs to have to be allowed to post new topics via email"
     email_in_category: "The category new emails are posted into"
     email_prefix: "The [label] used in the subject of emails. It will default to 'title' if not set"
+    email_site_title: "The title of the site used as the sender of emails from the site. Default to 'title' if not set. If your 'title' contains characters that are not allowed in email sender strings, use this setting."
 
     minimum_topics_similar: "How many topics need to exist in the database before similar topics are presented."
 

config/site_settings.yml

@@ -385,6 +385,7 @@ email:
     enum: 'MinTrustToCreateTopicSetting'
   email_in_category: -1
   email_prefix: ''
+  email_site_title: ''
 
 files:
   max_image_size_kb:

lib/email/message_builder.rb

@@ -168,7 +168,7 @@ module Email
     end
 
     def site_alias_email(source)
-      "#{SiteSetting.title} <#{source}>"
+      "#{SiteSetting.email_site_title.presence || SiteSetting.title} <#{source}>"
     end
 
   end