Why SendGrid Emails Go to Spam and How to Fix It

SendGrid emails usually go to spam because authentication, alignment, list quality or sending pattern is wrong, not because SendGrid is broken. If you keep increasing volume before fixing the cause, mailbox providers usually filter harder. This guide gives you the checks, DNS fixes, SendGrid settings, warm-up rules and proof steps.

If you are setting up from scratch, keep the SendGrid warm-up guide open beside this fix. Before changing records, check the sending domain with the free SPF checker, DKIM checker and DMARC checker.

Why are SendGrid emails going to spam?

Start with the symptom. Spam placement is rarely one isolated failure. It is usually a stack of small problems that receiving providers score together.

SendGrid Activity is useful, but it is not an inbox placement report. A delivered event means the recipient server accepted the message. It does not mean the message reached the primary inbox.

Which numbers matter?

Use numbers to decide whether you have a setup problem, a reputation problem or a volume problem. Where a provider does not publish a number, do not invent one. Use the provider’s current documentation and your own logs.

For primary guidance, read Google email sender guidelines, Yahoo sender best practices and Microsoft’s current sender requirements when you send at that scale.

Is SendGrid authentication passing?

Authentication is the first place to look because it is objective. Either the record exists and passes, or it does not.

Authenticate the SendGrid domain

In SendGrid, go to Settings → Sender Authentication → Authenticate Your Domain. Choose your DNS host, enter the domain or subdomain you will send from, and let SendGrid generate the DNS records.

SendGrid usually gives you CNAME records for domain authentication. The exact hostnames and targets are generated inside your account. Do not copy values from another domain or a blog post.

Publish the records at your DNS host. If you use Cloudflare, set these authentication records to DNS only, not proxied. A proxied mail authentication CNAME can break verification.

Then return to SendGrid and click Verify. SendGrid documents the flow in its domain authentication guide.

Single Sender Verification is not the same fix. It verifies one sending address, but it does not give your domain the same authentication foundation as full domain authentication.

Check SPF correctly

SPF authorises the service that sends mail for your domain. With SendGrid, the practical point is simple: the visible sending domain must authorise SendGrid through the records SendGrid asks you to publish.

Do not create multiple SPF TXT records at the root. A domain should have one SPF record beginning with v=spf1. If you already use Google Workspace, Zoho, Microsoft or another sender, merge includes into one record.

Also watch the SPF 10-DNS-lookup limit. Too many include mechanisms can cause SPF permerror, which looks like authentication failure to receivers. If you hit that, use the SPF lookup limit guide before adding another include.

Check DKIM selectors

DKIM signs mail with a key controlled by your domain. SendGrid domain authentication normally creates DKIM through CNAME records. Common selectors include s1 and s2, but your account can generate different values.

Open a test email in Gmail, choose Show original, and check DKIM. You want DKIM to pass with the same organisational domain as your From address, or an aligned domain under relaxed alignment.

If DKIM fails, check three things first. The record host may have been pasted with the full domain twice. The CNAME may be proxied. Or you may be sending from a different domain than the one you authenticated.

Publish DMARC

DMARC tells receivers what to do when SPF or DKIM fails alignment. For a repair phase, start with monitoring.

Replace example.com and the reporting mailbox. Once legitimate mail passes, you can move to a stricter policy. Do not jump to p=reject while you are still unsure whether all senders are authenticated.

Google and Yahoo expect DMARC for bulk senders. Yahoo requires DMARC at least p=none and passing, with From domain alignment through SPF or DKIM.

Which SendGrid settings should you fix?

DNS can pass while the sending setup still looks suspicious. The next checks are inside SendGrid and the message itself.

Use the right SMTP credentials

If an app sends through SendGrid SMTP, use SendGrid’s documented SMTP settings. The host is smtp.sendgrid.net. The username is apikey, and the password is your SendGrid API key. Use TLS on a supported port, commonly 587.

SendGrid lists SMTP integration details in its SMTP service documentation. Avoid using a personal mailbox password or an unrelated SMTP host for the same From domain.

Brand your tracking links

Unbranded tracking links create a domain mismatch. The visible From domain says one thing, but links and redirects point somewhere else. That can hurt trust, especially on newer domains.

In SendGrid, use branded link tracking for the same domain family you send from. The exact DNS record is generated by SendGrid. It is usually a CNAME under a branded tracking subdomain.

If you do not need click tracking, turn it off while diagnosing. A plain link to your own domain is easier to evaluate than a chain of redirects.

Match your From identity

Use a From address on the authenticated domain. Avoid sending from sales@example.com through an authenticated domain like mail.otherdomain.com unless alignment is deliberate and tested.

The envelope sender, DKIM signing domain and visible From domain do not need to be identical in every case. But they need to align under provider rules. When fixing spam placement, simpler is better.

Use a stable From name as well. Changing the From name, subdomain and template at the same time makes reputation harder to read.

Add unsubscribe handling

If you send marketing or bulk mail, include a working unsubscribe link. For Gmail and Yahoo bulk expectations, one-click unsubscribe applies to subscribed promotional mail.

Cold email still needs a clear opt-out process. BobWork Outbound adds a List-Unsubscribe header and link for its own campaigns. If you send directly through SendGrid, configure this in your sending app or template.

Honour unsubscribes quickly. Yahoo’s published best practices say to honour them within 2 days.

Is the list causing spam placement?

Authentication gets you through the door. List quality and content decide whether recipients trust the mail.

Stop bad segments first

If a segment produces bounces, spam complaints or no engagement, stop it before you fix anything else. Continuing to send while debugging pollutes the reputation data.

Export recent SendGrid Activity and look at blocks, bounces, spam reports and invalid emails. Then check SendGrid suppressions. Suppressed contacts should not be re-uploaded to another campaign tool.

Never use purchased or scraped lists for permission-based marketing. For cold outreach, keep targeting narrow and relevant. Generic high-volume blasts create the same negative signals even when DNS is perfect.

Simplify the email

For a repair test, send plain text or near-plain text. Use one clear link at most. Avoid URL shorteners, heavy HTML, image-only messages, attachments and misleading subject lines.

Spam filters do not use one magic word list. They evaluate the whole message and sender history. But a lightweight message gives you a cleaner test because it removes tracking, layout and link risk.

If transactional mail goes to spam, separate it from promotional campaigns. Use different categories, templates and ideally a different subdomain. Password resets should not share reputation with cold acquisition sequences.

Watch replies and complaints

Mailbox providers trust human behaviour. Replies, saves and normal conversation help. Complaints, deletes without reading and spam moves hurt.

Do not ask your team to mark spam as not spam on personal accounts at scale. That is not a repair strategy. Use controlled test inboxes to diagnose, then fix the cause.

For Gmail-heavy sending, set up Google Postmaster Tools. It can show domain reputation, spam rate and authentication status when there is enough mail volume for Google to report data.

When does warm-up help SendGrid?

Warm-up is useful when reputation is missing or stale. It is not a substitute for authentication, consent or list quality.

Use warm-up when the sending domain is new, the SendGrid dedicated IP is new, the mailbox identity has not sent before, or you are restarting after a long quiet period. Warm-up creates a gradual pattern instead of a sudden spike.

Do not use warm-up as a cover for broken DNS. If SPF, DKIM or DMARC fails, fix that first. Do not use warm-up to push bad lists, misleading offers or high-volume campaigns through a domain that is already receiving complaints.

BobWork Email Warm-up supports SendGrid by sending through your SendGrid SMTP credentials and checking received mail through an IMAP inbox. The free pool does this step automatically in a shared warm-up network, or you can switch to a private pool per account if you prefer.

The engine starts at 3 emails per day, adds 2 per day, and caps at 30 per day by default. Weekends run at 30%. Warm-up mail found in Spam is moved to Inbox, marked read, labelled Warm-up and archived after 24 hours. Only warm-up mail carrying the engine’s hidden header is touched.

For a broader decision, read does email warm-up work and domain warm-up vs mailbox warm-up.

What should you do now?

Work in this order. Objective fixes come first. Reputation work comes after setup is correct.

If your domain appears on a public blacklist, do not panic. Many listings do not affect every mailbox provider. Check the listing, identify the cause, and request delisting only after the underlying issue is fixed.

Confirm the fix worked

Do not confirm with one successful test. Spam filtering is probabilistic. You need a short run of clean sending.

Use three evidence sources. First, inspect message headers from Gmail, Yahoo and any important recipient domain. Authentication should pass consistently. Second, check SendGrid Activity for bounces, blocks and spam reports. Third, manually check controlled inboxes for Inbox, Promotions and Spam placement.

For Gmail, watch Google Postmaster Tools if you send enough volume for dashboards to populate. Keep the spam complaint rate under 0.1%, and never at 0.3%. Also watch domain reputation and authentication panels.

For Yahoo, keep SPF and DKIM passing, DMARC at least p=none, alignment working, one-click unsubscribe where required, and spam rate under 0.3%. Yahoo also expects unsubscribes to be honoured within 2 days.

For Microsoft consumer mailboxes, the published high-volume threshold is over 5,000 emails per day. At that level, SPF, DKIM and DMARC with alignment are required. Microsoft does not publish a numeric complaint threshold in the provided sender rule summary, so monitor blocks, replies and complaints rather than guessing one.

A clean repair window is typically seven days for an existing domain. For a new domain or new dedicated IP, give it two to three weeks. Keep real outreach around 30–50 emails per mailbox per day, and add mailboxes or domains instead of forcing more volume through one identity.

If you want a controlled ramp, connect SendGrid to BobWork Email Warm-up. It is free for up to 10 mailboxes on new accounts, with no credit card and no time limit. Use it after DNS is correct, not before. No warm-up tool can guarantee delivery, so keep watching real inbox placement.

Frequently asked questions