Log in to the Twilio SendGrid console, go to Marketing then Single Sends, click the title of the Single Send you want to test, type addresses under Test Your Email, and click Send Test Message.
Before you read what arrives, know that SendGrid changed it. The documentation is direct about this: Twilio SendGrid prepends Test - to the subject line, so recipients know the message is a test. That single behavior makes a quick test send unusable for judging the one part of your email a filter reads first. Your subject line is a scored input, and the subject line in your inbox is not the subject line you are about to send.
SendGrid is unusual among sending platforms in having a genuine spam test in the product at all. Most do not. That makes it worth being precise about what each of its three test surfaces actually measures.
| SendGrid feature | What it measures | Cost |
|---|---|---|
| Send Test Message | Layout and content, with Test - added to the subject | Free, no credits |
| Spam Test | The message against filtering criteria, as a report | One Email Testing credit |
| Inbox Rendering Test | Screenshots across email clients and devices | Email Testing credits |
| Link validation | Whether every URL in the message resolves | Free, bundled with rendering |
Send a quick test email in SendGrid
The quick path lives on the Single Send itself and needs no setup.
- Log in to the Twilio SendGrid console.
- Go to Marketing, then Single Sends.
- Click the title of the Single Send you want to test.
- Under Test Your Email, type the addresses that should receive the message.
- Click Send Test Message.
What lands is your content with a modified subject. Use it to check the layout, the copy and whether images load. Do not use it to evaluate the subject line, and do not draw conclusions about where a real campaign would land from where this one landed.
Run a Spam Test or an Inbox Rendering Test
The scored tests sit behind a different path, which is the most common reason people conclude SendGrid has no spam test.
- Go to Marketing, then Single Sends, then Settings, then Test Your Email.
- Click the title of the Single Send you want to test.
- Click Create Test.
- On the Select testing options page, choose the Spam Test, the Inbox Rendering Test, or both.
- Pick the clients you want rendered.
- Click Run Test.
SendGrid's documentation for this was last updated on 16 March 2026.
Email Testing credits expire every month
Both the Spam Test and the Inbox Rendering Test draw on Email Testing credits, and SendGrid states that all of them expire at the end of each month, whether they arrived with your plan or were purchased as an add-on package. How many you get depends on your Marketing Campaigns or Email API plan.
There is one free check in the set worth using every time. Every inbox rendering test run includes a link validation test that checks the validity of all URLs in the message, and SendGrid confirms these do not consume credits. That is not a trivial win: across messages tested with Unspam this year, 80% are clean of broken links, which means one campaign in five ships with a link that does not resolve.
A Spam Test scores the message, not the destination
A spam test reads what you wrote. It can tell you that your HTML is malformed, that a phrase is heavily weighted, that your text-to-image ratio is poor. Those are properties of the file.
Inbox placement is decided somewhere else, using inputs a content scan has no access to: your sending domain's reputation at that specific provider, your complaint rate there over recent weeks, how that provider's own users have engaged with your mail, and the authentication on the message as delivered. The same message routinely lands in the inbox at one provider and in spam at another, on the same day, from the same sender.
That gap is the reason a clean score and a placement problem coexist so often. Of the campaigns run through Unspam so far this year, 65% of emails reach the primary inbox, and the messages making up the other share are not, as a rule, badly written. The Unspam deliverability benchmark tracks the split. For what a score is and is not measuring, SpamAssassin scoring covers the mechanics in detail.
SendGrid Campaigns is now Single Sends, and the old docs are gone
Two changes inside about a year make most older SendGrid tutorials wrong in ways that are hard to spot. What used to be called a campaign is now a Single Send, and the documentation moved from docs.sendgrid.com to twilio.com/docs/sendgrid. Separately, SendGrid retired its free Email API and free Marketing Campaigns plans starting 27 May 2025.
If a guide tells you to open Campaigns, or links to a docs.sendgrid.com URL, it predates both and its click paths will not match your console.
Testing an API send, where the console tools do not reach
The test features described above are attached to Single Sends. If you send through the SendGrid API, none of them applies to your traffic, and the honest test is the message itself.
Send through your normal API path to an external address with sandbox mode switched off, then open the Activity Feed. The event to look for first is Dropped, which means SendGrid never attempted delivery at all. The usual cause is that the address sits on one of your own suppression lists from an earlier bounce or complaint, and no amount of filter analysis will explain a message that never left.
When you need a real send instead
Once the layout is right and the Spam Test is clean, the questions still open are all about the live send: whether your DKIM signature aligns to your own domain, whether your tracking links resolve through a domain with a clean history, and where the message actually lands per provider.
The SendGrid deliverability guide covers that setup, including the suppression behavior that quietly swallows test recipients. For the placement question, an inbox placement test delivers your campaign to seed mailboxes at Gmail, Outlook, Yahoo and five other providers and reports where each copy was filed.
When you have the message you plan to send, run it through the free Unspam spam test as it will actually go out, subject line included.
