diff --git a/dist.ini b/dist.ini
index eb00f9a..bd959d0 100644
--- a/dist.ini
+++ b/dist.ini
@@ -9,6 +9,7 @@ copyright_holder = Ricardo Signes
 Moo                    = 2.000000 ; do not apply fatal warnings to us!
 MooX::Types::MooseLike = 0.15     ; InstanceOf uses ->isa
 Throwable::Error = 0.200003       ; with $obj->throw and ->throw($str) and Moo
+Net::IDN::Encode = 0
 
 Net::SMTP = 3.07 ; SSL support, fixed datasend
 
diff --git a/lib/Email/Sender/Transport/SMTP.pm b/lib/Email/Sender/Transport/SMTP.pm
index 35a162b..28e3269 100644
--- a/lib/Email/Sender/Transport/SMTP.pm
+++ b/lib/Email/Sender/Transport/SMTP.pm
@@ -8,6 +8,7 @@ use Email::Sender::Success::Partial;
 use Email::Sender::Role::HasMessage ();
 use Email::Sender::Util;
 use MooX::Types::MooseLike::Base qw(Bool Int Str HashRef);
+use Net::IDN::Encode qw(domain_to_ascii);
 use Net::SMTP 3.07; # SSL support, fixed datasend
 
 use utf8 (); # See below. -- rjbs, 2015-05-14
@@ -105,7 +106,12 @@ has allow_partial_success => (is => 'ro', isa => Bool, default => sub { 0 });
 
 =cut
 
-has helo      => (is => 'ro', isa => Str);
+has helo => (
+    is => 'ro',
+    isa => Str,
+    coerce => sub { domain_to_ascii( $_[0] ) }
+);
+
 has localaddr => (is => 'ro');
 has localport => (is => 'ro', isa => Int);
 
diff --git a/t/smtp-via-mock.t b/t/smtp-via-mock.t
index c546cf6..16dacde 100644
--- a/t/smtp-via-mock.t
+++ b/t/smtp-via-mock.t
@@ -1,6 +1,7 @@
 #!perl
 use strict;
 use warnings;
+use utf8;
 use Test::More;
 
 BEGIN {
@@ -32,7 +33,7 @@ BEGIN {
   $mock_smtp->{failaddr}{'permfail@example.net'} = [ 519 => 'Permanent STHU' ];
 }
 
-plan tests => 95;
+plan tests => 97;
 
 use Email::Sender::Transport::SMTP;
 use Email::Sender::Transport::SMTP::Persistent;
@@ -348,6 +349,16 @@ for my $class (qw(
       },
     );
   }
+
+  {
+    local $test   = 'helo idn conversion';
+    local $sender = $class->new({
+      helo => 'Bücher.ch',
+    });
+
+    is($sender->helo, 'xn--bcher-kva.ch', 'IDN conversion successful');
+  }
+
 }
 
 subtest "quoteaddr" => sub {