diff --git a/mailer.rb b/mailer.rb
index 4f8b1a7..0df603f 100644
--- a/mailer.rb
+++ b/mailer.rb
@@ -14,13 +14,13 @@ require 'tempfile'
 # Load environment variables from.env file
 Dotenv.load
 
-DB_URL = ENV.fetch('DATABASE_URL')
+DB_URL = ENV.fetch('DATABASE_URL', nil)
 
-DB_USER = ENV.fetch('DB_USER')
-DB_PASSWORD = ENV.fetch('DB_PASSWORD')
-DB_HOST = ENV.fetch('DB_HOST')
-DB_PORT = ENV.fetch('DB_PORT')
-DB_NAME = ENV.fetch('DB_NAME')
+DB_USER = ENV.fetch('DB_USER', nil)
+DB_PASSWORD = ENV.fetch('DB_PASSWORD', nil)
+DB_HOST = ENV.fetch('DB_HOST', nil)
+DB_PORT = ENV.fetch('DB_PORT', nil)
+DB_NAME = ENV.fetch('DB_NAME', nil)
 
 SMTP_SERVER = ENV.fetch('SMTP_SERVER')
 SMTP_PORT = ENV.fetch('SMTP_PORT').to_i
@@ -37,8 +37,9 @@ Here are the titles that were listened to this week
 END
 
 def fetch_titles_from_db()
+  raise "Please set either DATABASE_URL or DB_USER..." if DB_USER.nil? && DB_URL.nil?
   one_week_ago = Date.today - 7
-  connection = DB_URL ? PG.connect(DB_URL) : PG.connect(:dbname => DB_NAME, :host => DB_HOST, :user => DB_USER, :password => DB_PASSWORD)
+  connection = !DB_URL.nil? ? PG.connect(DB_URL) : PG.connect(:dbname => DB_NAME, :host => DB_HOST, :user => DB_USER, :password => DB_PASSWORD)
 
   result = connection.exec_params("SELECT item_title FROM activities WHERE created_at >= $1 ORDER BY created_at DESC", [one_week_ago])
   connection.close