ActionMailer errors on ruby-1.9.1-p376

Can't duplicate. Which mail version you have bundled?

mail-1.6.0 and mail-1.5.4 raises the same error for me.

1) Error: test_decode_message_with_incorrect_charset(ActionMailerTest):
ArgumentError: invalid byte sequence in US-ASCII

/Users/tchandy/Projetos/OpenSource/rails/vendor/gems/ruby/1.9.1/gems/mail-1.6.0/lib/mail/core_extensions/string.rb:4:in `gsub'
/Users/tchandy/Projetos/OpenSource/rails/vendor/gems/ruby/1.9.1/gems/mail-1.6.0/lib/mail/core_extensions/string.rb:4:in `to_crlf'
/Users/tchandy/Projetos/OpenSource/rails/vendor/gems/ruby/1.9.1/gems/mail-1.6.0/lib/mail/message.rb:1428:in `raw_source='
/Users/tchandy/Projetos/OpenSource/rails/vendor/gems/ruby/1.9.1/gems/mail-1.6.0/lib/mail/message.rb:1517:in `init_with_string'
/Users/tchandy/Projetos/OpenSource/rails/vendor/gems/ruby/1.9.1/gems/mail-1.6.0/lib/mail/message.rb:106:in `initialize'
/Users/tchandy/Projetos/OpenSource/rails/vendor/gems/ruby/1.9.1/gems/mail-1.6.0/lib/mail/mail.rb:50:in `new'
/Users/tchandy/Projetos/OpenSource/rails/vendor/gems/ruby/1.9.1/gems/mail-1.6.0/lib/mail/mail.rb:50:in `new'
/Users/tchandy/Projetos/OpenSource/rails/actionmailer/test/mail_service_test.rb:875:in `test_decode_message_with_incorrect_charset'
/Users/tchandy/Projetos/OpenSource/rails/vendor/gems/ruby/1.9.1/gems/mocha-0.9.8/lib/mocha/integration/mini_test/version_131_and_above.rb:27:in `run'

2) Error: test_decode_message_with_unknown_charset(ActionMailerTest):
ArgumentError: invalid byte sequence in US-ASCII

/Users/tchandy/Projetos/OpenSource/rails/vendor/gems/ruby/1.9.1/gems/mail-1.6.0/lib/mail/core_extensions/string.rb:4:in `gsub'
/Users/tchandy/Projetos/OpenSource/rails/vendor/gems/ruby/1.9.1/gems/mail-1.6.0/lib/mail/core_extensions/string.rb:4:in `to_crlf'
/Users/tchandy/Projetos/OpenSource/rails/vendor/gems/ruby/1.9.1/gems/mail-1.6.0/lib/mail/message.rb:1428:in `raw_source='
/Users/tchandy/Projetos/OpenSource/rails/vendor/gems/ruby/1.9.1/gems/mail-1.6.0/lib/mail/message.rb:1517:in `init_with_string'
/Users/tchandy/Projetos/OpenSource/rails/vendor/gems/ruby/1.9.1/gems/mail-1.6.0/lib/mail/message.rb:106:in `initialize'
/Users/tchandy/Projetos/OpenSource/rails/vendor/gems/ruby/1.9.1/gems/mail-1.6.0/lib/mail/mail.rb:50:in `new'
/Users/tchandy/Projetos/OpenSource/rails/vendor/gems/ruby/1.9.1/gems/mail-1.6.0/lib/mail/mail.rb:50:in `new'
/Users/tchandy/Projetos/OpenSource/rails/actionmailer/test/mail_service_test.rb:1034:in `test_decode_message_with_unknown_charset'
/Users/tchandy/Projetos/OpenSource/rails/vendor/gems/ruby/1.9.1/gems/mocha-0.9.8/lib/mocha/integration/mini_test/version_131_and_above.rb:27:in `run'

3) Error: test_decode_message_without_content_type(ActionMailerTest):
ArgumentError: invalid byte sequence in US-ASCII

/Users/tchandy/Projetos/OpenSource/rails/vendor/gems/ruby/1.9.1/gems/mail-1.6.0/lib/mail/core_extensions/string.rb:4:in `gsub'
/Users/tchandy/Projetos/OpenSource/rails/vendor/gems/ruby/1.9.1/gems/mail-1.6.0/lib/mail/core_extensions/string.rb:4:in `to_crlf'
/Users/tchandy/Projetos/OpenSource/rails/vendor/gems/ruby/1.9.1/gems/mail-1.6.0/lib/mail/message.rb:1428:in `raw_source='
/Users/tchandy/Projetos/OpenSource/rails/vendor/gems/ruby/1.9.1/gems/mail-1.6.0/lib/mail/message.rb:1517:in `init_with_string'
/Users/tchandy/Projetos/OpenSource/rails/vendor/gems/ruby/1.9.1/gems/mail-1.6.0/lib/mail/message.rb:106:in `initialize'
/Users/tchandy/Projetos/OpenSource/rails/vendor/gems/ruby/1.9.1/gems/mail-1.6.0/lib/mail/mail.rb:50:in `new'
/Users/tchandy/Projetos/OpenSource/rails/vendor/gems/ruby/1.9.1/gems/mail-1.6.0/lib/mail/mail.rb:50:in `new'
/Users/tchandy/Projetos/OpenSource/rails/actionmailer/test/mail_service_test.rb:869:in `test_decode_message_without_content_type'
/Users/tchandy/Projetos/OpenSource/rails/vendor/gems/ruby/1.9.1/gems/mocha-0.9.8/lib/mocha/integration/mini_test/version_131_and_above.rb:27:in `run'

143 tests, 385 assertions, 0 failures, 3 errors, 0 skips
rake aborted!
Command failed with status (1): [/Users/tchandy/.rvm/ruby-1.9.1-p376/bin/ru...]

(See full trace by running task with --trace)

Can you put the email that raised the error as an attachment?

You can sanitise it first, but try not to change the contents (charsets) too much.

Mikel