emails: use separate addresses for different types of emails.

app/mailers/user_mailer.rb

@@ -5,24 +5,44 @@ class UserMailer < ApplicationMailer
   def dmail_notice(dmail)
     @dmail = dmail
     @user = dmail.to
-    mail(@user, require_verified_email: true, subject: "#{Danbooru.config.app_name}: #{dmail.from.name} sent you a message")
+    mail(
+      @user,
+      from: "#{Danbooru.config.canonical_app_name} <#{Danbooru.config.notification_email}>",
+      subject: "#{Danbooru.config.canonical_app_name}: #{dmail.from.name} sent you a message",
+      require_verified_email: true,
+    )
   end
 
   # The email sent when a user requests a password reset.
   def password_reset(user)
     @user = user
-    mail(@user, require_verified_email: false, subject: "#{Danbooru.config.app_name} password reset request")
+    mail(
+      @user,
+      from: "#{Danbooru.config.canonical_app_name} <#{Danbooru.config.account_security_email}>",
+      subject: "#{Danbooru.config.app_name} password reset request",
+      require_verified_email: false,
+    )
   end
 
   # The email sent when a user changes their email address.
   def email_change_confirmation(user)
     @user = user
-    mail(@user, require_verified_email: false, subject: "Confirm your email address")
+    mail(
+      @user,
+      from: "#{Danbooru.config.canonical_app_name} <#{Danbooru.config.account_security_email}>",
+      subject: "Confirm your email address",
+      require_verified_email: false,
+    )
   end
 
   # The email sent when a new user signs up with an email address.
   def welcome_user(user)
     @user = user
-    mail(@user, require_verified_email: false, subject: "Welcome to #{Danbooru.config.app_name}! Confirm your email address")
+    mail(
+      @user,
+      from: "#{Danbooru.config.canonical_app_name} <#{Danbooru.config.welcome_user_email}>",
+      subject: "Welcome to #{Danbooru.config.app_name}! Confirm your email address",
+      require_verified_email: false,
+    )
   end
 end

config/danbooru_default_config.rb

@@ -15,7 +15,7 @@
 # and add DANBOORU_ to the front. More examples:
 #
 #     DANBOORU_CANONICAL_URL=https://booru.example.com
-#     DANBOORU_CONTACT_EMAIL=admin@borou.example.com
+#     DANBOORU_CONTACT_EMAIL=admin@booru.example.com
 #     DANBOORU_DISCORD_SERVER_URL=https://discord.gg/yourbooru
 #
 # Settings from environment variables will override those from the config file.
@@ -86,11 +86,26 @@ module Danbooru
       "http://#{Danbooru.config.hostname}"
     end
 
-    # Contact email address of the admin.
+    # The email address of the admin user. This email will be publicly displayed on the contact page.
     def contact_email
       "webmaster@#{Danbooru.config.hostname}"
     end
 
+    # The email address to use for Dmail notifications.
+    def notification_email
+      "notifications@#{Danbooru.config.hostname}"
+    end
+
+    # The email address to use for password reset and email verification emails.
+    def account_security_email
+      "security@#{Danbooru.config.hostname}"
+    end
+
+    # The email address to use for new user signup emails.
+    def welcome_user_email
+      "welcome@#{Danbooru.config.hostname}"
+    end
+
     # System actions, such as sending automated dmails, will be performed with
     # this account. This account must have Moderator privileges.
     #