pythonワンライナーでテスト用のsmtpサーバーを立てる方法 python -m smtpd -n -c DebuggingServer localhost:20025 telnetで接続してみる $ telnet localhost 20025 Trying ::1... telnet: connect to address ::1: Connection refused Trying 127.0.0.1... Connected to localhost. Escape character is '^]'. 220 macbookpro.local Python SMTP proxy version 0.2 HELO 127.0.0.1 250 mackbookpro.local MAIL FROM: foo@example.com 250 Ok RCPT TO: bar@exam