[smtp] cmd

# base
smtp (simple mail transfer protocol)

# telnet
telnet <host> // port: 23
telnet <host> <port>
telnet localhost 25 // enter interactive interface

# interactive (with hMailServer)
220 xxx ESMTP // xxx is server name
EHLO yyy // yyy is client domain name (or ex. EHLO HelloWorld)
250-xxx
250-SIZE 20480000
250-AUTH LOGIN
250 HELP
HELP
211 DATA HELO EHLO MAIL NOOP QUIT RCPT RSET SAML TURN VRFY
NOOP
250 OK
VRFY [email protected]
502 VRFY disallowed.
RCPT TO: <[email protected]>
503 must have sender first.
DATA
503 Must have sender and recipient first.
MAIL FROM: <[email protected]> // MAIL FROM: [email protected] (ok), MAIL FROM:[email protected] (ok)
250 OK
MAIL FROM: <[email protected]>
503 Issue a reset if you want to start over
RSET
250 OK
MAIL FROM: <[email protected]> // if the mail address doesn't exist in 'Domains', it is considered as a 'external e-mail address', otherwise it is a "local e-mail address"
250 OK
RCPT TO: <[email protected]> // if the mail address doesn't exist in 'Domains', it is considered as a 'external e-mail address', otherwise it is a "local e-mail address"
530 SMTP authentication is required. // according to MAIL FROM & RCPT TO & 'Require SMTP authentication' (Settings > Advanced > IP Ranges > (mateched high priority) > Require SMTP authentication)
RSET
MAIL FROM: <test@thishost>
250 OK
RCPT TO: <[email protected]>
250 OK
DATA
354 OK, send.
Subject: Test Mail
From: [email protected] // the mail address just shows on the mail
To: [email protected] // the mail address just shows on the mail
  // need a empty line
This is a test email sent via Telnet.
. // DATA finish
250 Queued (zzz seconds)
QUIT // close interactive interface
221 goodbye

Connection to host lost.

# interactive command
HELO (Hello)
EHLO (Extended Hello)
NOOP (No Operation)
RSET (Reset)
VRFY (Verify)

# in hMailServer, 530 SMTP authentication is required
AUTH LOGIN
334 VXNlcm5hbWU6 // VXNlcm5hbWU6 is the base64 of Username:
dGVzdEBsb2NhbGhvc3Q= // dGVzdEBsb2NhbGhvc3Q= is the base64 of test@localhost
334 UGFzc3dvcmQ6 // UGFzc3dvcmQ6 is the base64 of Password:
MVFhejJ3c3g= // MVFhejJ3c3g= is the base64 of 1Qaz2wsx
235 authenticated.
=> ref: https://blog.csdn.net/FunchMin/article/details/106958118
=> ref: https://mailtrap.io/blog/smtp-auth/

# in hMailServer, log file
| Settings > Logging
check 'Enabled'
check 'SMTP'
C:\Program Files (x86)\hMailServer\Logs\

# in hMailServer, IP Ranges
| Settings > Advanced > IP Ranges
- Priority
    a higher value means higher priority
- Lower ip & Upper ip
    for matching smtp client ip
- Require SMTP authentication
    if the 'MAIL FROM' mail address doesn't exist in 'Domains', it is considered as a 'external e-mail address', otherwise it is a "local e-mail address"
    if the 'RCPT TO' mail address doesn't exist in 'Domains', it is considered as a 'external e-mail address', otherwise it is a "local e-mail address"
    'External to external e-mail address' should normally always be selected (if you do not require authentication when external users sends messages through your server, your server will be abused by spammers)
=> ref: https://www.hmailserver.com/documentation/latest/?page=reference_iprange

# in hMailServer, reset administrator password
C:\Program Files (x86)\hMailServer\Bin\hMailServer.INI
[Security]
AdministratorPassword=7cba6767a5489b002c08bdb068cac033 // 7cba6767a5489b002c08bdb068cac033 is the MD5 of 1Qaz2wsx

# in hMailServer, ide vs. server
hMailServer Administrator (ide)
hMailServer (server)

like
SQL Server Management Studio (ide)
SQL Server (server)

# outlook
openssl s_client -starttls smtp -connect smtp.office365.com:587

(interactive)
EHLO a.com
250-TYCP286CA0083.outlook.office365.com Hello [60.248.96.211]
250-SIZE 157286400
250-PIPELINING
250-DSN
250-ENHANCEDSTATUSCODES
250-AUTH LOGIN XOAUTH2
250-8BITMIME
250-BINARYMIME
250-CHUNKING
250 SMTPUTF8
AUTH LOGIN
334 VXNlcm5hbWU6
<username-base64-string>
334 UGFzc3dvcmQ6
<app-password-base64-string>
235 2.7.0 Authentication successful
MAIL FROM: <[email protected]>
250 2.1.0 Sender OK
RCPT TO: <[email protected]> // 240B0000:error:0A00010A:SSL routines:can_renegotiate:wrong ssl version:ssl\ssl_lib.c:2289:
rcpt to: <[email protected]> // ok
250 2.1.5 Recipient OK
DATA
354 Start mail input; end with <CRLF>.<CRLF>
Subject: Test Mail
From: [email protected]
To: [email protected]
  // need a empty line
This is a test email sent via openssl. (outlook)
. // DATA finish
250 2.0.0 OK <AS8P251MB0086A13302184C6CA3DE6D72F18C2@AS8P251MB0086.EURP251.PROD.OUTLOOK.COM> [Hostname=AS8P251MB0086.EURP251.PROD.OUTLOOK.COM]auth

IMPORTANT. microsoft app password
https://support.microsoft.com/en-us/account-billing/how-to-get-and-use-app-passwords-5896ed9b-4263-e681-128a-a6f2979a7944

# gmail
openssl s_client -starttls smtp -connect smtp.gmail.com:587

(interactive)
EHLO a.com
250-smtp.gmail.com at your service, [60.248.96.211]
250-SIZE 35882577
250-8BITMIME
250-AUTH LOGIN PLAIN XOAUTH2 PLAIN-CLIENTTOKEN OAUTHBEARER XOAUTH
250-ENHANCEDSTATUSCODES
250-PIPELINING
250-CHUNKING
250 SMTPUTF8
AUTH LOGIN
334 VXNlcm5hbWU6
<username-base64-string>
334 UGFzc3dvcmQ6
<app-password-base64-string>
235 2.7.0 Accepted
MAIL FROM: <[email protected]>
250 2.1.0 OK 98e67ed59e1d1-2d41ee18656sm3331866a91.13 - gsmtp
RCPT TO: <[email protected]> // 4C4A0000:error:0A00010A:SSL routines:can_renegotiate:wrong ssl version:ssl\ssl_lib.c:2289:
rcpt to: <[email protected]> // ok
250 2.1.5 OK 98e67ed59e1d1-2d41ee18656sm3331866a91.13 - gsmtp
DATA
354  Go ahead 98e67ed59e1d1-2d41ee18656sm3331866a91.13 - gsmtp
Subject: Test Mail
From: [email protected]
To: [email protected]
  // need a empty line
This is a test email sent via openssl. (gmail)
. // DATA finish
250 2.0.0 OK  1724052123 98e67ed59e1d1-2d41ee18656sm3331866a91.13 - gsmtp

IMPORTANT. google app password
https://stackoverflow.com/a/60718806/6751999