# SMTP 指令測試 ###### tags: `smtp` 記錄一下測試SMTP的指令。 一般 smtp 用 telnet ```bash= $ telnet smtp.gmail.com:25 Trying 142.251.8.109... Connected to smtp.gmail.com. Escape character is '^]'. 220 smtp.gmail.com ESMTP e14sm5278155pfv.18 - gsmtp EHLO 10.123.6.70 250-smtp.gmail.com at your service, [123.204.7.189] 250-SIZE 35882577 250-8BITMIME 250-STARTTLS 250-ENHANCEDSTATUSCODES 250-PIPELINING 250-CHUNKING 250 SMTPUTF8 ``` startls 用 openssl 指令 ```bash= $ openssl s_client -starttls smtp -connect smtp.gmail.com:25 CONNECTED(00000005) depth=2 C = US, O = Google Trust Services LLC, CN = GTS Root R1 verify return:1 depth=1 C = US, O = Google Trust Services LLC, CN = GTS CA 1C3 verify return:1 depth=0 CN = smtp.gmail.com verify return:1 --- Certificate chain 0 s:CN = smtp.gmail.com i:C = US, O = Google Trust Services LLC, CN = GTS CA 1C3 1 s:C = US, O = Google Trust Services LLC, CN = GTS CA 1C3 i:C = US, O = Google Trust Services LLC, CN = GTS Root R1 2 s:C = US, O = Google Trust Services LLC, CN = GTS Root R1 i:C = BE, O = GlobalSign nv-sa, OU = Root CA, CN = GlobalSign Root CA --- read R BLOCK 250-smtp.gmail.com at your service, [123.204.7.189] 250-SIZE 35882577 250-8BITMIME 250-AUTH LOGIN PLAIN XOAUTH2 PLAIN-CLIENTTOKEN OAUTHBEARER XOAUTH 250-ENHANCEDSTATUSCODES 250-PIPELINING 250-CHUNKING 250 SMTPUTF8 ``` tls ```bash= openssl s_client -connect smtp.gmail.com:465 ``` 在公司網路測試連不上