The Google Script extracts the content of a Google Documents, converts the styles as inline CSS using the MailChimp API and send the document via Gmail as HTML Mail.

Sends an email using the contents of a Google Document as the body.

function sendDocument(documentId, recipient, subject) {
  var html = convertToHtml(documentId);
  html = inlineCss(html);
  GmailApp.sendEmail(recipient, subject, null, {
    htmlBody: html,
  });
}

Converts a file to HTML.

The Advanced Drive service must be enabled to use this function.

function convertToHtml(fileId) {
  var file = Drive.Files.get(fileId);
  var htmlExportLink = file.exportLinks['text/html'];
  if (!htmlExportLink) {
    throw 'File cannot be converted to HTML.';
  }
  var oAuthToken = ScriptApp.getOAuthToken();
  var response = UrlFetchApp.fetch(htmlExportLink, {
    headers: {
      Authorization: 'Bearer ' + oAuthToken,
    },
    muteHttpExceptions: true,
  });
  if (!response.getResponseCode() == 200) {
    throw 'Error converting to HTML: ' + response.getContentText();
  }
  return response.getContentText();
}

Inlines CSS within an HTML file using the MailChimp API.

To use the API you must register for an account and then copy your API key into the script property “mailchimp.apikey”.

function inlineCss(html) {
  var apikey = CacheService.getPublicCache().get('mailchimp.apikey');
  if (!apikey) {
    apikey = PropertiesService.getScriptProperties().getProperty('mailchimp.apikey');
    CacheService.getPublicCache().put('mailchimp.apikey', apikey);
  }
  var datacenter = apikey.split('-')[1];
  var url = Utilities.formatString('https://%s.api.mailchimp.com/2.0/helper/inline-css', datacenter);
  var response = UrlFetchApp.fetch(url, {
    method: 'post',
    payload: {
      apikey: apikey,
      html: html,
      strip_css: true,
    },
  });
  var output = JSON.parse(response.getContentText());
  if (!response.getResponseCode() == 200) {
    throw 'Error inlining CSS: ' + output['error'];
  }
  return output['html'];
}