Emails supporting ESMTP Authentication

Using system. net. Mail. smtpclient under. NET Framework can easily send emails, but many email servers now support ESMTP protocol. The biggest difference between ESMTP and ESMTP is that the account and password must be provided for verification during sending. ESMTP sends commands in a stream to interact with the server to send and receive emails. For more SMTP commands, see: http://www.magicwinmail.com/technic_smtp.php

 

The following is a simple example: (no judgment or encapsulation is made for reference only)

Code

  String  SMTP  =     "Mail.com  "  ;
  String From  =     Send@mail.com  "  ;
  String  PWD  =     "Pwd  "  ;
  String  To  =     Rec@mail.com "  ;

  //  Create Link  
  Tcpclient TC  =     New  Tcpclient (SMTP,  25  );
  Byte  [] B  =     New    Byte  [  1024  ];
TC. getstream (). Read (B,  0  , B. Length );
Response. Write (encoding. utf8.getstring (B)  +  "  <Br/>  "  );

  //  Identity  
  Writemsg (TC. getstream (), "  Helo XXXX \ r \ n  "  );
Response. Write (readmsg (TC. getstream ())  +     "  <Br/>  "  );

  //  Authentication starts  
  Writemsg (TC. getstream (),  "  Auth login \ r \ n "  );
Response. Write (readmsg (TC. getstream ())  +     "  <Br/>  "  );

  //  Account base64 encoding  
    Byte  [] Btxt  =  New    Byte  [  1024  ];
Btxt  =  Encoding. utf8.getbytes (from );
Writemsg (TC. getstream (), convert. tobase64string (btxt)  +  "  \ R \ n  "  );
Response. Write (readmsg (TC. getstream ())  +     "  <Br/> "  );

  //  Base64 encoding  
  Btxt  =  Encoding. utf8.getbytes (PWD );
Writemsg (TC. getstream (), convert. tobase64string (btxt)  +     "  \ R \ n  "  );
Response. Write (readmsg (TC. getstream ())  +    "  <Br/>  "  );
  //  Authentication completed

  //  Email sending Address  
  Writemsg (TC. getstream (),  String  . Format (  "  Mail from: {0} \ r \ n  " , From ));
Response. Write (readmsg (TC. getstream ())  +     "  <Br/>  "  );

  //  Accept email address, which can have multiple RCPT  
  Writemsg (TC. getstream (),  String  . Format (  "  Rcpt to: {0} \ r \ n  " , ));
Response. Write (readmsg (TC. getstream ())  +     "  <Br/>  "  );

  //  Ru Hua  
  Writemsg (TC. getstream (),  "  Data \ r \ n  "  );
Response. Write (readmsg (TC. getstream ()) +     "  <Br/>  "  );

  //  Email content  
  Stringbuilder sb  =     New  Stringbuilder ();
SB. appendformat (  "  From: {0} \ r \ n  " , From );  //  Sender  
  SB. appendformat (  "  To: {0} \ r \ n  "  , );  //  There can be multiple recipients separated by semicolons. These two lines can be different from the preceding mail from and rcpt to (displayed in the mail content)  
  SB. appendformat (  "  Date: {0} \ r \ n  " , Datetime. Now. tostring ());  //  Time  
  SB. appendformat (  "  Subject: {0} \ r \ n  "  ,  "  Test  "  );  //  Topic  
  SB. append ( "  \ R \ n  "  );
SB. append (  "  Content  "  );  //  Body  
  SB. append (  "  \ R \ n. \ r \ n  "  );

Writemsg (TC. getstream (), SB. tostring ());
Response. Write (readmsg (TC. getstream ()) +     "  <Br/>  "  );

  //  End session  
  Writemsg (TC. getstream (),  "  Quit  "  );

  //  Close link  
 TC. Close (); 

 

Code

  Private     Void  Writemsg (networkstream NS,  String  MSG)
{
  Byte  [] BW  =  Encoding. utf8.getbytes (MSG );
NS. Write (BW, 0  , BW. Length );
}
  Private     String  Readmsg (networkstream NS)
{
  Byte  [] Br  =     New     Byte  [  1024  ];
NS. Read (BR,  0 , Br. Length );
  Return  Encoding. utf8.getstring (BR );
} 

 

 

If the operation is normal, the returned status is as follows:

 
  220 mail.com ESMTP CMailServer 5.4.6 SMTP Service ready
250 welcome here
334 vxnlcm5hbwu6
334 ugfzc3dvcmq6
235 OK
250 OK
250 OK
354 send the mail data, end.
250 OK
 

 

We should be familiar with the SMTP protocol and related commands, and send data in the format to interact with the server. Note the space in the center of the command and the CRLF at the end (Press enter to wrap the line ).

 
Tags: SMTP, ESMTP, email, email, identity authentication
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