MAILTOOL has had the ability when sending emails to let you specify multiple mail routers in case of a failure.  Be sure to click on the link to see how that works if you are unfamiliar with this excellent and unique option included with MAILTOOL.

With v11.20 and up MAILTOOL now allows you to also specify *G4GSMAIL as a mail router and an option to send emails using the GreenTools for Google Apps Send Email Addon.

See the following JSON routers file as an example of how you can specify G4GSMAIL to be used to send email if a previous router fails:

{
  "mail_routers": [

    {
      "mail_router": "smtp.gmail.com",
      "from_email": "bvstone@bvstools.com",
      "perform_mx_lookup": "*NO",
      "use_ssl": "*TLS",
      "smtp_port" : "587",
      "smtp_auth_user" : "bvstone@bvstools.com",
      "smtp_auth_password" : "thisisnotmyrealpassword",
      "sequence": 10
    },
    {
      "mail_router": "*G4GSMAIL",
      "sequence": 20
    },
    {
      "mail_router": "smtp.gmail.com",
      "from_email": "bvstone@gmail.com",
      "perform_mx_lookup": "*NO",
      "use_ssl": "*TLS",
      "smtp_port" : "587",
      "smtp_auth_user" : "bvstone",
      "smtp_auth_password" : "thisisafakepassword",
      "sequence": 40
    },
    {
      "mail_router": "smtp.office365.com",
      "from_email": "bvstone@bvstools.onmicrosoft.com",
      "perform_mx_lookup": "*NO",
      "use_ssl": "*TLS",
      "smtp_port" : "587",
      "smtp_auth_user" : "bvstone@bvstools.onmicrosoft.com",
      "smtp_auth_password" : "notmyrealpassword",
      "sequence": 50
    },
    {
      "mail_router": "smtp-mail.outlook.com",
      "from_email": "bvstone@outlook.com",
      "perform_mx_lookup": "*NO",
      "use_ssl": "*TLS",
      "smtp_port" : "587",
      "smtp_auth_user" : "*G4MS_XOAUTH2",
      "sequence": 60
    }
  ]
}

So, as you can see the sequence 20 in this list is simply the value *G4GSMAIL for the mail_router.  This will signal MAILTOOL to use the #g4gmail_sendMail() API included with the G4G Send Email Addon product.  Of course your G4G library will need to be in the library list when using this option as well and it will use the FROM address as the account, so that will need to be set up prior as well.

Feel free to contact us with any questions.  Thank you!