我正在运行mailcatcher以查看通过smtp在Rails项目上发送的邮件，但在我的机器上发送我收到的电子邮件时：
Net::SMTPFatalError (550 Message rejected)
邮件仍显示在mailcatcher中，但看起来文本显示为附件而不是html。
如果我在前台mailcatcher -f -v中运行带有详细模式的mailcatcher，我会得到以下堆栈跟踪：
Exception: undefined method `match' for nil:NilClass
Backtrace:
/Users/matt/.rvm/gems/ruby-1.9.3-p194@merchant_messaging/gems/mail-2.4.4/lib/mail/utilities.rb:104:in `unbracket'
/Users/matt/.rvm/gems/ruby-1.9.3-p194@merchant_messaging/gems/mail-2.4.4/lib/mail/part.rb:29:in `cid'
/Users/matt/.rvm/gems/ruby-1.9.3-p194@merchant_messaging/gems/mailcatcher-0.5.10/lib/mail_catcher/mail.rb:51:in `block in add_message'
/Users/matt/.rvm/gems/ruby-1.9.3-p194@merchant_messaging/gems/mailcatcher-0.5.10/lib/mail_catcher/mail.rb:48:in `each'
/Users/matt/.rvm/gems/ruby-1.9.3-p194@merchant_messaging/gems/mailcatcher-0.5.10/lib/mail_catcher/mail.rb:48:in `add_message'
/Users/matt/.rvm/gems/ruby-1.9.3-p194@merchant_messaging/gems/mailcatcher-0.5.10/lib/mail_catcher/smtp.rb:45:in `receive_message'
/Users/matt/.rvm/gems/ruby-1.9.3-p194@merchant_messaging/gems/eventmachine-1.0.0/lib/em/protocols/smtpserver.rb:532:in `process_data_line'
/Users/matt/.rvm/gems/ruby-1.9.3-p194@merchant_messaging/gems/eventmachine-1.0.0/lib/em/protocols/smtpserver.rb:196:in `receive_line'
/Users/matt/.rvm/gems/ruby-1.9.3-p194@merchant_messaging/gems/eventmachine-1.0.0/lib/em/protocols/linetext2.rb:64:in `receive_data'
/Users/matt/.rvm/gems/ruby-1.9.3-p194@merchant_messaging/gems/eventmachine-1.0.0/lib/em/protocols/linetext2.rb:65:in `receive_data'
/Users/matt/.rvm/gems/ruby-1.9.3-p194@merchant_messaging/gems/eventmachine-1.0.0/lib/em/protocols/linetext2.rb:65:in `receive_data'
/Users/matt/.rvm/gems/ruby-1.9.3-p194@merchant_messaging/gems/eventmachine-1.0.0/lib/em/protocols/linetext2.rb:65:in `receive_data'
/Users/matt/.rvm/gems/ruby-1.9.3-p194@merchant_messaging/gems/eventmachine-1.0.0/lib/em/protocols/linetext2.rb:65:in `receive_data'
/Users/matt/.rvm/gems/ruby-1.9.3-p194@merchant_messaging/gems/eventmachine-1.0.0/lib/eventmachine.rb:187:in `run_machine'
/Users/matt/.rvm/gems/ruby-1.9.3-p194@merchant_messaging/gems/eventmachine-1.0.0/lib/eventmachine.rb:187:in `run'
/Users/matt/.rvm/gems/ruby-1.9.3-p194@merchant_messaging/gems/mailcatcher-0.5.10/lib/mail_catcher.rb:134:in `run!'
/Users/matt/.rvm/gems/ruby-1.9.3-p194@merchant_messaging/gems/mailcatcher-0.5.10/bin/mailcatcher:4:in `<top (required)>'
/Users/matt/.rvm/gems/ruby-1.9.3-p194@merchant_messaging/bin/mailcatcher:19:in `load'
/Users/matt/.rvm/gems/ruby-1.9.3-p194@merchant_messaging/bin/mailcatcher:19:in `<main>'
显然我不是唯一一个有这个问题的人。有关详细信息，请参阅此github问题https://github.com/sj26/mailcatcher/issues/73。