SMTP

1
SMTP

• CS176A
• Ramya Raghavendra
• ramya_at_cs.ucsb.edu

2
SMTP

• What is SMTP?
• Simple Mail Transfer Protocol
• SMTP server every email client interfaces to
  send email
• List of SMTP servers in transit - Check the
  headers on your email!
• Why talk directly to SMTP server?
• Automation of emails in applications
• Without dependency on another email client
• Real time notification of status
• Wrong ID, passwords etc

3
Example

• Consider Windows alternative like MAPI
• More complex
• More overhead

4
Multipart Messages

• But can we send multipart messages with
  attachments?
• YES
• SMTP is only a delivery mechanism, nothing to do
  with contents
• RFCs on how to create multipart messages with
  attachments
• Your assignment
• Simple text

5
SMTP commands
6
For testing purposes

• Part 1
• Please note NO TURNIN
• Part 2
• To command line argument
• Subject cs176aHW3ProgPart2
• Content Name and Perm no.

7
Email Sender Logic

• / open the network connection /
• sfd smtpConnect(smtp_server,smtp_port)
• if (sfd INVALID_SOCKET)
• rc(-1)
• goto cleanup
• // Send HELO
• smtpHelo(sfd,helo_domain)
• //Send From address
• smtpMailFrom(sfd,from)
• //Send To address
• smtpRcptTo(sfd)

8
Email Sender Logic (Cont)

• //Send Data
• smtpData(sfd)
• //Send End-of-mail .
• smtpEom(sfd)
• //Send QUIT
• smtpQuit(sfd)

9
Connection to SMTP Server

• / connect to SMTP server and returns the socket
  fd /
• static SOCKET smtpConnect (char smtp_server, int
  port)
• SOCKET
• sfd
• sfdclientSocket(smtp_server,port)
• if (sfd INVALID_SOCKET)
• errorMsg("Could not connect to SMTP
  server \"s\" at port d\n",
• smtp_server,port)
• return (INVALID_SOCKET)
• / save it. we'll need it to clean up /
• smtp_socketsfd
• return (sfd)

10
One example

• / SMTP HELO /
• static int smtpHelo(int sfd,char helo_domain)
• memset(buf,0,sizeof(buf))
• (void) snprintf(buf,sizeof(buf)-1,"HELO
  s\r\n",helo_domain)
• //Socket write function
• sockPuts(sfd,buf)
• return (smtpResponse(sfd))