I have simplified the module to this: #!/usr/bin/perl use Net::FTP; $ftp = Net::FTP->new("9.9.9.9 5000", Debug => 0) or die "Cannot connect to some.host.name: $@"; $ftp->login("Domain\\user1",'password321') or die "Cannot login ", $ftp->message; $ftp->quit; for the domain I have tried: Domain\user Domain\\user Domain\/user Domain/user Nothing will work guys. Error received: Cannot login Invalid userid/password