{"id":24385,"date":"2024-09-17T22:17:18","date_gmt":"2024-09-17T22:17:18","guid":{"rendered":"https:\/\/www.gmass.co\/blog\/?p=24385"},"modified":"2026-08-05T19:04:05","modified_gmt":"2026-08-05T19:04:05","slug":"transactional-emails-api","status":"publish","type":"post","link":"https:\/\/www.gmass.co\/blog\/transactional-emails-api\/","title":{"rendered":"How to Send Transactional Emails with the GMass API"},"content":{"rendered":"<p>You can <a href=\"https:\/\/www.gmass.co\/blog\/api-create-send-campaign\/\">send full-fledged email campaigns using the GMass API<\/a>.<\/p>\n<p>But\u2026 you can also <strong>use the GMass API to send single, one-off messages<\/strong>\u00a0through your Gmail\/Google Workspace account.<\/p>\n<p>Those are <a href=\"https:\/\/www.gmass.co\/features\/gmail-transactional-emails\">transactional emails<\/a>; emails that go out immediately after, generally, a user takes an action.<\/p>\n<p>In this guide, I\u2019ll expand on the <a href=\"https:\/\/api.gmass.co\/docs\">GMass API docs<\/a>\u00a0to dig deeper into the <strong>process of sending a transactional email<\/strong>.<\/p>\n<p>By sending transactional emails through the GMass API, your messages are <strong>sent through your Gmail\/Google Workspace account<\/strong>.<\/p>\n<p>That means you\u2019ll find them in your <strong>Gmail Sent folder<\/strong>\u00a0(which is great for searchability or <a href=\"https:\/\/www.gmass.co\/features\/gmail-list-builder\">future list building<\/a>). And they&#8217;re still <strong>trackable<\/strong> inside GMass<\/p>\n<p>Here\u2019s how to send them.<\/p>\n<h2 id=\"send-transactional-e-cedy\">Send Transactional Emails with the GMass API: Table of Contents<\/h2>\n<ul>\n<li><a href=\"#getting-your-api-key-ywuy\">Getting Your API Key and Using it to Authenticate Into the API<\/a><\/li>\n<li id=\"getting-your-api-key-ywuy\"><a href=\"#composing-and-sendin-dnlr\">Composing and Sending Your Transactional Email<\/a><\/li>\n<li><a href=\"#optional-settings-fo-onhp\">Optional Settings for Transactional Emails Through the GMass API<\/a><\/li>\n<li><a href=\"#ready-to-send-transa-iwhw\">Ready to Send Transactional Emails Using the GMass API?<\/a><\/li>\n<\/ul>\n<h2>Getting Your API Key and Using it to Authenticate Into the API<\/h2>\n<p>To use the GMass API you\u2019ll need to generate or retrieve a key, then pass it to GMass.<\/p>\n<h3 id=\"generating-or-retrie-ygfh\">Generating or retrieving your API key<\/h3>\n<p>Go to the <strong>GMass <\/strong><strong><a href=\"https:\/\/gmass.co\/dashboard\">dashboard<\/a><\/strong>. Click on the <strong>Settings<\/strong>\u00a0icon on the top right. In the left fly-out panel, scroll down to <strong>API Keys<\/strong>, then click into that section and click on <strong>Manage API Keys<\/strong>.<\/p>\n<figure style=\"text-align: center;\"><img decoding=\"async\" src=\"https:\/\/www.gmass.co\/blog\/wp-content\/uploads\/2024\/09\/apitransaction-managekeys.png\" alt=\"Going to the manage API keys section of the GMass dashboard.\" \/><\/figure>\n<p>If you don\u2019t have any API keys generated already, <strong>click on the red button to create one<\/strong>. (If you already have a key, you can always make a new one as well for this particular project.)<\/p>\n<figure style=\"text-align: center;\"><img decoding=\"async\" src=\"https:\/\/www.gmass.co\/blog\/wp-content\/uploads\/2024\/09\/apitransaction-createkey.png\" alt=\"Create a new API key\" \/><\/figure>\n<p>Now you\u2019ll be able to <strong>copy that API key<\/strong>\u00a0by clicking the clipboard icon to its right.<\/p>\n<p>If you ever need this key again, you can come back to this part of the GMass dashboard to grab it.<\/p>\n<figure style=\"text-align: center;\"><img decoding=\"async\" src=\"https:\/\/www.gmass.co\/blog\/wp-content\/uploads\/2024\/09\/apitransaction-copyapikey.png\" alt=\"Copying your API key\" \/><\/figure>\n<h3 id=\"using-your-api-key-f-kknz\">Using your API key for authentication<\/h3>\n<p>There are two ways you can pass your API key to GMass.<\/p>\n<p>Option 1: You can pass your key with a HTTP header, using X-apikey.<\/p>\n<p>Option 2: You can include it as a query string after you call any GMass API endpoint by adding apikey=<em>your API key<\/em>.<\/p>\n<p>Every GMass API endpoint starts with https:\/\/api.gmass.co\/api\/. For transactional emails, you could use <code>https:\/\/api.gmass.co\/api\/transactional?apikey=whatever-whatever-whatever-whatever<\/code>.<\/p>\n<p>For my examples in this article I\u2019m using the <a href=\"https:\/\/api.gmass.co\/apihelp\/index#\/\">Swagger site<\/a>\u00a0for the GMass API. If you want to run tests there yourself, just <strong id=\"composing-and-sendin-dnlr\">paste your API key in the form field<\/strong>\u00a0on the top right of the page.<\/p>\n<h2>Composing and Sending Your Transactional Email<\/h2>\n<p>There\u2019s only one transactional email method in the GMass API which keeps this process relatively simple.<\/p>\n<p>Using the transactional email endpoint, you\u2019ll <strong>need to designate a fromEmail, fromName, to, subject, and message<\/strong>.<\/p>\n<p>You can put <strong>multiple addresses in the to: field<\/strong>; just separate them with commas or semicolons.<\/p>\n<p>All other parameters are optional.<\/p>\n<p>Your message can be plain text or include HTML elements as you put it together for the <strong>message<\/strong>\u00a0parameter.<\/p>\n<figure style=\"text-align: center;\"><img decoding=\"async\" src=\"https:\/\/www.gmass.co\/blog\/wp-content\/uploads\/2024\/09\/apitransaction-sendmessage.png\" alt=\"The basic parameters for sending a transactional email via the GMass API\" \/><\/figure>\n<p>And the result:<\/p>\n<figure style=\"text-align: center;\"><img decoding=\"async\" src=\"https:\/\/www.gmass.co\/blog\/wp-content\/uploads\/2024\/09\/apitransaction-headers.png\" alt=\"The sent message and headers\" \/><\/figure>\n<p>So\u2026 that\u2019s pretty much it. I\u2019m going to cover the optional settings next but really, from here <strong id=\"optional-settings-fo-onhp\">you\u2019re already good to go on sending one-off transactional emails<\/strong>\u00a0via the GMass API.<\/p>\n<p>That was fast.<\/p>\n<h2>Optional Settings for Transactional Emails Through the GMass API<\/h2>\n<p>There are a handful of optional settings you can use as you fine-tune your transactional emails.<\/p>\n<p>Before I get into them, it\u2019ll be helpful to briefly cover the <strong>relationship between the transactional email and GMass\u2019s transactional SMTP relay service<\/strong>.<\/p>\n<h3 id=\"the-gmass-transactio-momz\">The GMass transactional email API powers GMass\u2019s transactional SMTP relay service<\/h3>\n<p>For those unfamiliar, GMass offers all subscribers a <a href=\"https:\/\/www.gmass.co\/blog\/introducing-smtp-service\/\">transactional email SMTP relay<\/a>, smtp.gmass.co, for lower-volume transactional emailers.<\/p>\n<p>This service actually <em>uses<\/em>\u00a0the GMass transactional API method to send those messages.<\/p>\n<p>So when you\u2019re sending transactional emails via the API, you\u2019re skipping the whole relay step and just getting down to the roots.<\/p>\n<p>This will come up a bit as we go through the optional settings \u2014 especially if you\u2019ve been using the GMass transactional SMTP relay.<\/p>\n<h3 id=\"optional-open-and-cl-fqyy\">Optional open and click tracking<\/h3>\n<p>GMass <strong>can include open and\/or click tracking<\/strong>\u00a0on the transactional emails you send through the GMass API.<\/p>\n<p>If you\u2019d like to do so, set the <strong>openTrack<\/strong>\u00a0and\/or <strong>clickTrack<\/strong>\u00a0to parameters to <strong>true<\/strong>.<\/p>\n<p>Note: For click tracking, you\u2019ll need to send an HTML email where you link a word or words. For example, <code>&lt;a href=\u201dhttps:\/\/whatever.com\u201d&gt;click here\u201d&lt;\/a&gt;<\/code>. Straight URLs, like <code>https:\/\/www.whatever.com<\/code>, are not trackable. Quick explanation: We can\u2019t replace a URL with a tracking link, as it\u2019s a big spam red flag to put a URL in an email and have it link to a different destination.<\/p>\n<p>Another note: <strong>If you use the GMass transactional SMTP relay and you\u2019ve designated tracking settings in the GMass dashboard<\/strong>, the settings here are <em>unrelated <\/em>to those. So if you have open tracking turned on for emails with the transactional SMTP relay but, for your application using the API, you have openTrack set to false, opens will not be tracked.<\/p>\n<p>If you have a <a href=\"https:\/\/www.gmass.co\/blog\/tracking-domain\/\">custom tracking domain<\/a>\u00a0set up in the GMass dashboard, it will be used for your tracking links.<\/p>\n<figure style=\"text-align: center;\"><img decoding=\"async\" src=\"https:\/\/www.gmass.co\/blog\/wp-content\/uploads\/2024\/09\/apitransaction-openclicktrue.png\" alt=\"Setting open and click tracking via the API\" \/><\/figure>\n<p>And the result:<\/p>\n<figure style=\"text-align: center;\"><img decoding=\"async\" src=\"https:\/\/www.gmass.co\/blog\/wp-content\/uploads\/2024\/09\/apitransaction-openclickresult.png\" alt=\"A transactional email sent with open and click tracking\" \/><\/figure>\n<p>You can see the <strong>analytics from all your transactional emails<\/strong>\u00a0in the GMass dashboard. On the main screen of the dashboard there\u2019s a tab where you can check the details of your transactional emails.<\/p>\n<figure style=\"text-align: center;\"><img decoding=\"async\" src=\"https:\/\/www.gmass.co\/blog\/wp-content\/uploads\/2024\/09\/apitransaction-analytics.png\" alt=\"Checking the analytics of transactional emails in the GMass dashboard\" \/><\/figure>\n<h3 id=\"using-your-own-smtp-lgav\">Using your own SMTP<\/h3>\n<p>By default, GMass will send the transactional emails through your Gmail account, and with that, through Google&#8217;s servers.<\/p>\n<p>However, <strong>if you\u2019d like to send through your own SMTP service<\/strong>, you have that option as well with the <strong>useCustomerSmtp<\/strong>\u00a0parameter.<\/p>\n<p><strong>Make sure you have a SMTP server set up in the GMass dashboard<\/strong>; that will be the SMTP service that GMass uses if you set this parameter to true.<\/p>\n<p>And if you&#8217;ve <a href=\"https:\/\/www.gmass.co\/blog\/dkim-settings\/\">configured DKIM in your account settings<\/a>, your transactional emails will now be DKIM signed.<\/p>\n<p>If you set the useCustomerSmtp parameter to <strong>true<\/strong>\u00a0and do not have a SMTP server connected to your GMass account, the API will error out.<\/p>\n<figure style=\"text-align: center;\"><img decoding=\"async\" src=\"https:\/\/www.gmass.co\/blog\/wp-content\/uploads\/2024\/09\/apitransaction-smtpserver.png\" alt=\"Using an SMTP server\" \/><\/figure>\n<p>I am on GMass\u2019s in-house SMTP server here. That\u2019s <em>different<\/em>\u00a0from our transactional SMTP relay service. Here\u2019s a helpful article on the <a href=\"https:\/\/www.gmass.co\/blog\/smtp-options\/\">various SMTP offerings from GMass<\/a>\u00a0if you\u2019d like more details (and disambiguation) on all the options.<\/p>\n<p>You may\u2019ve noticed another parameter here in the \/api\/transactional endpoint called <strong>smtpRelay<\/strong>. You do <strong>not<\/strong>\u00a0need to set that, and it won\u2019t affect anything if you do. That parameter is for internal use when someone is sending through the API via the GMass transactional SMTP relay.<\/p>\n<p>To demonstrate using a SMTP server, I\u2019ll send transactional emails to GMass\u2019s free <a href=\"https:\/\/www.gmass.co\/analyze\">email analyzer<\/a>\u00a0tool with <strong>useCustomerSmtp<\/strong>\u00a0set to both true and false.<\/p>\n<p>Here\u2019s the result when I set useCustomerSmtp to true. The email goes through my designated SMTP service:<\/p>\n<figure style=\"text-align: center;\"><img decoding=\"async\" src=\"https:\/\/www.gmass.co\/blog\/wp-content\/uploads\/2024\/09\/apitransaction-myserveranalysis.png\" alt=\"A transactional email sent through an SMTP server\" \/><\/figure>\n<p>And here\u2019s the result when I set useCustomerSmtp to false. The email goes through Google\u2019s servers:<\/p>\n<figure style=\"text-align: center;\"><img decoding=\"async\" src=\"https:\/\/www.gmass.co\/blog\/wp-content\/uploads\/2024\/09\/apitransaction-googleserveranalysis.png\" alt=\"A transactional email sent through Gmail\" \/><\/figure>\n<h3 id=\"threading-to-a-prior-mxzv\">Threading to a prior campaign<\/h3>\n<p>The last parameter we\u2019ll cover is <strong>threadToCampaign<\/strong>, which enables you to <strong>send your transactional email as a reply to a prior campaign<\/strong>.<\/p>\n<p>You can get the ID of the previous campaign in a variety of ways, like checking the campaign analytics or via the GMass dashboard. You can also get campaign IDs through the GMass API, using the \/api\/campaigns endpoint.<\/p>\n<figure style=\"text-align: center;\"><img decoding=\"async\" src=\"https:\/\/www.gmass.co\/blog\/wp-content\/uploads\/2024\/09\/apitransaction-threadtocampaign.png\" alt=\"Threading to a campaign\" \/><\/figure>\n<p>That transactional email will now go out like a reply to that campaign in the same thread.<\/p>\n<figure style=\"text-align: center;\"><img decoding=\"async\" src=\"https:\/\/www.gmass.co\/blog\/wp-content\/uploads\/2024\/09\/apitransaction-threadresult.png\" alt=\"The result for a threaded transactional email sent through the GMass API\" \/><\/figure>\n<p>And as you can see, I <strong id=\"ready-to-send-transa-iwhw\">still had to set a subject for the transactional email<\/strong>\u00a0in the API \u2014 but <strong>it\u2019s not included here<\/strong>\u00a0as the message went out as a reply.<\/p>\n<h3>Unsubscribe and bounce lists<\/h3>\n<p>The transactional email system will check addresses against your <a href=\"https:\/\/www.gmass.co\/blog\/unsubscribes-api\/\">unsubscribe<\/a> and <a href=\"https:\/\/www.gmass.co\/blog\/advanced-bounce-handling\/\">bounce<\/a> lists in GMass and suppress any emails to people who&#8217;ve opted out or bounced in the past.<\/p>\n<h2>Ready to Send Transactional Emails Using the GMass API?<\/h2>\n<p>As I said earlier, sending a transactional email with the GMass API is <strong>really not a complicated process<\/strong>.<\/p>\n<ul>\n<li>Use the <strong>\/api\/transactional endpoint<\/strong>\u00a0to <strong>create and send<\/strong>\u00a0your message.<\/li>\n<li>Set any <strong>optional settings<\/strong>\u00a0you might want like open\/click tracking, whether to send through a SMTP server or not, and threading to prior campaigns.<\/li>\n<\/ul>\n<p>If you\u2019re <strong>ready to use the GMass API to send transactional emails<\/strong>\u00a0from your own applications, good news: Full API access is included in GMass\u2019s <strong>Premium<\/strong>, <strong>Professional<\/strong>, and <strong>Team<\/strong>\u00a0plans.<\/p>\n<p>(You can find pricing info for those on the <a href=\"https:\/\/www.gmass.co\/pricing\">GMass pricing<\/a>\u00a0page.)<\/p>\n<p>And with all those plans <strong>you can also send full email campaigns inside Gmail<\/strong>\u00a0using the <a href=\"https:\/\/chrome.google.com\/webstore\/detail\/gmass-powerful-mail-merge\/ehomdgjhgmbidokdgicgmdiedadncbgf\">GMass Chrome extension<\/a>.<\/p>\n<p>With <strong>unlimited emails, campaigns, and contacts<\/strong>, see why <strong>400,000+ people<\/strong>\u00a0love GMass and have given us an average of <strong>4.8 out of 5 stars<\/strong>\u00a0across tens of thousands of reviews.<\/p>\n<p>You can <strong>try GMass for free<\/strong>\u00a0with <strong>no credit card required<\/strong>.<\/p>\n<p><a href=\"https:\/\/chrome.google.com\/webstore\/detail\/gmass-powerful-mail-merge\/ehomdgjhgmbidokdgicgmdiedadncbgf\">Download the Chrome extension<\/a>\u00a0and you\u2019ll be up and running \u2014 and ready to use the API \u2014 in a matter of minutes.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>You can send full-fledged email campaigns using the GMass API. But\u2026 you can also use the GMass API to send single, one-off messages\u00a0through your Gmail\/Google Workspace account. Those\u2026<\/p>\n","protected":false},"author":29,"featured_media":24389,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[9152,2723],"tags":[],"class_list":["post-24385","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-api","category-smtp"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v28.3 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\r\n<title>How to Send Transactional Emails with the GMass API<\/title>\r\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\r\n<link rel=\"canonical\" href=\"https:\/\/www.gmass.co\/blog\/transactional-emails-api\/\" \/>\r\n<meta property=\"og:locale\" content=\"en_US\" \/>\r\n<meta property=\"og:type\" content=\"article\" \/>\r\n<meta property=\"og:title\" content=\"How to Send Transactional Emails with the GMass API\" \/>\r\n<meta property=\"og:description\" content=\"You can send full-fledged email campaigns using the GMass API. But\u2026 you can also use the GMass API to send single, one-off messages\u00a0through your Gmail\/Google Workspace account. Those\u2026\" \/>\r\n<meta property=\"og:url\" content=\"https:\/\/www.gmass.co\/blog\/transactional-emails-api\/\" \/>\r\n<meta property=\"og:site_name\" content=\"GMass Blog\" \/>\r\n<meta property=\"article:publisher\" content=\"https:\/\/www.facebook.com\/GmailMailMerge\/\" \/>\r\n<meta property=\"article:published_time\" content=\"2024-09-17T22:17:18+00:00\" \/>\r\n<meta property=\"article:modified_time\" content=\"2026-08-05T19:04:05+00:00\" \/>\r\n<meta property=\"og:image\" content=\"https:\/\/www.gmass.co\/blog\/wp-content\/uploads\/2024\/09\/apitransactional-feat-tinified.png\" \/>\r\n\t<meta property=\"og:image:width\" content=\"2002\" \/>\r\n\t<meta property=\"og:image:height\" content=\"934\" \/>\r\n\t<meta property=\"og:image:type\" content=\"image\/png\" \/>\r\n<meta name=\"author\" content=\"Sam Greenspan\" \/>\r\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\r\n<meta name=\"twitter:creator\" content=\"@GMassForGmail\" \/>\r\n<meta 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