Send mail to GMail using Indy

Once you've moved your email accounts to GMail (or even entire domains), you have to fix the code you use in your Delphi programs for generating and sending email automatically. In fact, GMail uses the SMTP protocol for sending email, but with a specific form of SSH encryption called TLS.

To make things even more complicated, different clients use different ports and configurations. In particular, Outlook (which providees no TLS support) has different settings. For Indy, you can follow the settings used by other client programs, like those provided for Thunderbird. More info on the various ports in this newsgroup post:

Gmail uses 25, 465 and 587 for SMTP, but since almost all isps block 25, 465 is the preferred SMTP with SSL for gmail, and 587 is the preferred SMTP with TLS port.

Here is the code of a demo program, with the DFM file and the actual Delphi code (which is the same you'd generally use):

  object IdSMTP1: TIdSMTP
    OnStatus = IdSMTP1Status
    IOHandler = IdSSLIOHandlerSocketOpenSSL1
    Host = 'smtp.gmail.com'
    Password = '***'
    Port = 587
    SASLMechanisms = <>
    UseTLS = utUseExplicitTLS
    Username = '****'
  end
  object IdSSLIOHandlerSocketOpenSSL1: TIdSSLIOHandlerSocketOpenSSL
    Destination = 'smtp.gmail.com:587'
    Host = 'smtp.gmail.com'
    MaxLineAction = maException
    Port = 587
    SSLOptions.Method = sslvTLSv1
    SSLOptions.Mode = sslmUnassigned
    SSLOptions.VerifyMode = []
    SSLOptions.VerifyDepth = 0
    OnStatusInfo = IdSSLIOHandlerSocketOpenSSL1StatusInfo
  end
      

      IdSMTP1.Connect;
      IdSMTP1.Send(IdMessage1);
      IdSMTP1.Disconnect;
      

Where IdMessage1 is the message you want to send. Of course, you can both send messages to your gmail account or to any other account from you GMail account.

Notice: If you don't use "explicit TLS" you'll have to make extra initialization calls (like: IdSMTP1.SendCmd('STARTTLS', 220);). Finally, the IdSSLIOHandlerSocketOpenSSL1StatusInfo event handler produces a report like this:

      SSL status: "before/connect initialization"
      SSL status: "before/connect initialization"
      SSL status: "SSLv3 write client hello A"
      SSL status: "SSLv3 read server hello A"
      SSL status: "SSLv3 read server certificate A"
      SSL status: "SSLv3 read server done A"
      SSL status: "SSLv3 write client key exchange A"
      SSL status: "SSLv3 write change cipher spec A"
      SSL status: "SSLv3 write finished A"
      SSL status: "SSLv3 flush data"
      SSL status: "SSLv3 read finished A"
      SSL status: "SSL negotiation finished successfully"
      status: "SSL negotiation finished successfully"
      Cipher: name = [...]; description = [...] SSLv3 Kx=RSA Au=RSA  Enc=3DES(168)