diff --git a/lib/noosfero/constants.rb b/lib/noosfero/constants.rb
index b587fd4..e1d97c7 100644
--- a/lib/noosfero/constants.rb
+++ b/lib/noosfero/constants.rb
@@ -1,5 +1,5 @@
 module Noosfero::Constants
-  EMAIL_FORMAT = /\A([^@\s]+)@((?:[-a-z0-9]+\.)+[a-z]{2,})\Z/i
+  EMAIL_FORMAT = /\A([^@\s]+)@((?:[-_a-z0-9]+\.)+[a-z]{2,})\Z/i
   INTEGER_FORMAT = /\A\d*\Z/i
   PROFILE_PER_PAGE = 10
 end
--
libgit2 0.21.2