diff --git a/actionmailer/lib/action_mailer/base.rb b/actionmailer/lib/action_mailer/base.rb
index b77409b..000c05d 100644
--- a/actionmailer/lib/action_mailer/base.rb
+++ b/actionmailer/lib/action_mailer/base.rb
@@ -674,7 +674,7 @@ module ActionMailer #:nodoc:
       def perform_delivery_smtp(mail)
         destinations = mail.destinations
         mail.ready_to_send
-        sender = (mail['return-path'] && mail['return-path'].spec) || mail.from
+        sender = (mail['return-path'] && mail['return-path'].spec) || mail['from']
 
         smtp = Net::SMTP.new(smtp_settings[:address], smtp_settings[:port])
         smtp.enable_starttls_auto if smtp_settings[:enable_starttls_auto] && smtp.respond_to?(:enable_starttls_auto)