Why your emails go to spam and how to fix it

When your business emails land in the customer's spam folder, the most common reason is that your domain does not prove the email really came from you. Gmail and Outlook check this with three records called SPF, DKIM and DMARC. Missing or wrong records, spam complaints and bad mailing lists are the usual causes. On cPanel email hosting, most of it is a few minutes' work.

What Gmail and Outlook check

Google says every sender to Gmail must set up SPF or DKIM, send over a secure connection, and keep the spam complaint rate below 0.3%. Senders of more than 5,000 emails a day to Gmail also need DMARC and a one-click unsubscribe link. Microsoft has similar rules for Outlook.com and Hotmail: big senders must pass SPF and DKIM and have a DMARC record. Mail that fails can go to Junk or be refused.

In plain words:

• SPF is a list of the servers allowed to send email for your domain.
• DKIM is a digital signature on each email, so the receiver knows it was not changed on the way.
• DMARC tells receivers what to do with email that fails those checks, and sends you reports.

The rules in 2026: failing mail is now refused

The big change is what happens to mail that fails. Google says that since November 2025 Gmail has been stepping up enforcement: messages that do not meet its sender rules can now get temporary or permanent rejections, so they may never reach the inbox or the spam folder at all. Microsoft does the same for large senders to Outlook.com and Hotmail. Mail that fails its checks bounces back with the error "550 5.7.515".

The check that catches most companies is the match between the address people see and the records. The domain in the "From" address must be the same domain that passes SPF or DKIM. Sending as info@yourcompany.com.my through a newsletter tool or a website plugin that signs with its own domain fails this check, even when SPF and DKIM pass for that other domain.

If a customer says they never got your email, ask for the bounce message. A code with 5.7.26 from Gmail or 5.7.515 from Outlook means an authentication problem, not a full mailbox.

Other common reasons

• You send newsletters from your normal mailbox to a big list, and people mark them as spam.
• Your list has old or wrong addresses, so many emails bounce.
• The "From" address does not match your domain, for example a website form that sends as a Gmail address.
• Someone broke into one of your mailboxes and is sending spam from it. That damages the whole domain.

What to do

1. Log in to cPanel and open Email Deliverability. It shows whether SPF and DKIM are set up for each domain, and offers a fix button when a record is missing or wrong.
2. If your domain's DNS is managed somewhere else (for example Cloudflare), copy the suggested records there instead.
3. Add a DMARC record. A starting policy of "none" only collects reports and does not block anything. Our support team can help you set it.
4. Send newsletters through a proper mailing service with an unsubscribe link, not from your daily mailbox. Set the service up to sign with your own domain (it will give you DKIM records to add), so the "From" address matches.
5. Clean your mailing list: remove addresses that bounce and people who did not ask to hear from you.
6. Use strong passwords and two-step login on every mailbox, so no one can send spam in your name.
7. Send yourself a test email at a Gmail address. In Gmail, open the message, click the three dots and choose "Show original". SPF, DKIM and DMARC should all say PASS.

Still going to spam after these steps? Contact our support team with an example email and we will look at it with you.

How SyncTech can help

If the records look right and mail still bounces, our email troubleshooting checklist lists the next things to check. For mailboxes with spam and virus filtering and a local support team, see our anti-spam email hosting.

Updated 26 October 2026: added the 2026 enforcement rules (Gmail and Outlook now refuse failing mail) and the "From" address match check.

Source and credit

We are sharing guidance from Google, Microsoft and Yahoo. This guide is written by Synctech in our own words.

• Email sender guidelines, Gmail Help (Google): https://support.google.com/a/answer/81126
• Email sender guidelines FAQ, Google Workspace Admin Help: https://support.google.com/a/answer/14229414
• Fix NDR error "550 5.7.515" in Outlook.com, Microsoft Support: https://support.microsoft.com/en-us/outlook/fix-ndr-error-550-5-7-515-in-outlook-com
• Sender best practices, Yahoo Sender Hub: https://senders.yahooinc.com/best-practices/

Retrieved 26 October 2026. Gmail, Outlook, Yahoo and cPanel are trademarks of their owners. Synctech is not connected with them. This is general information, not legal, tax or financial advice. If anything here is wrong, email support@synctech.com.my and we will correct it.