请问 got response code 451, with response: 451 5.7.3 STARTTLS is required to send mail 应该如何处理?
DEBUG SMTP: connected to host "mail.xxxx.net", port: 25 EHLO CNSHA0702A.ad001.siemens.net 250-mail.xxx.net Hello [111.1x1.109.xx] 250-SIZE 31457280 250-PIPELINING 250-DSN 250-ENHANCEDSTATUSCODES 250-STARTTLS
250-8BITMIME 250-BINARYMIME
250 CHUNKING
DEBUG SMTP: Found extension "SIZE", arg "31457280"
DEBUG SMTP: Found extension "PIPELINING", arg ""
DEBUG SMTP: Found extension "DSN", arg ""
DEBUG SMTP: Found extension "ENHANCEDSTATUSCODES", arg ""
DEBUG SMTP: Found extension "STARTTLS", arg ""
DEBUG SMTP: Found extension "8BITMIME", arg ""
DEBUG SMTP: Found extension "BINARYMIME", arg ""
DEBUG SMTP: Found extension "CHUNKING", arg ""
DEBUG SMTP: use8bit false
MAIL FROM:<sescs@xxxx.com>
451 5.7.3 STARTTLS is required to send mail DEBUG SMTP: got response code 451, with response: 451 5.7.3 STARTTLS is required to send mail