Even legitimate emails from real businesses get blocked or flagged as spam. This happens because receiving mail servers score every incoming message based on dozens of signals before deciding whether to deliver, quarantine, or reject it. This article explains why blocking happens and what you can do to fix it.

Why legitimate emails get blocked

Mail servers and spam filters do not know your intentions — they judge your email based on measurable signals. The most common reasons legitimate emails are blocked:

• Missing or broken SPF, DKIM, or DMARC records — the most common cause. Without these, receiving servers cannot verify that you are who you say you are.
• Shared IP reputation — on shared hosting, your email leaves the same IP address used by all other customers on that server. If another customer has been sending spam, the IP's reputation may already be damaged.
• No sending history on a new domain — new domains have zero reputation. Filters are naturally suspicious of them.
• High spam complaint rate — if enough recipients click "Mark as Spam," your sender score drops quickly.
• Sending to invalid or unclean lists — high bounce rates signal to filters that your list is poorly maintained.
• Spam-trigger words in subject or body — certain words and patterns are flagged by content filters.
• No reverse DNS (rDNS) — if the IP address your server sends from does not have a matching PTR record, many servers will reject the message outright.
• Missing unsubscribe link — required by law for commercial email, and its absence raises spam filter scores.

Step 1 — Fix your email authentication records

This is the single most impactful thing you can do. Set up all three:

• SPF — tells receiving servers which IP addresses are allowed to send email for your domain. See: How to Set Up an SPF Record in cPanel
• DKIM — adds a cryptographic signature to every outgoing email so receivers can verify it has not been tampered with. See: How to Set Up DKIM in cPanel
• DMARC — ties SPF and DKIM together and tells receivers what to do when authentication fails. See: How to Set Up DMARC

In cPanel, go to Email → Email Deliverability and click Repair for your domain. cPanel will create or fix SPF and DKIM automatically.

Step 2 — Check if your IP is blacklisted

1. Find your server's outgoing mail IP. In cPanel, go to Server Information or ask TPC Hosting support.
2. Go to https://mxtoolbox.com/blacklists.aspx and enter your IP address.
3. The tool checks over 100 blacklists simultaneously and shows which ones your IP appears on.

If your IP is blacklisted, see Step 5 on how to get delisted.

Step 3 — Test your overall sending score

Use https://mail-tester.com to get a spam score out of 10 for your emails:

1. The site gives you a unique test email address.
2. Send a real email from your domain to that address — use the same content and subject line you normally send.
3. Go back to mail-tester.com and click Check your score.
4. You will receive a detailed breakdown showing exactly what is hurting your score and what to fix.

Aim for a score of 9/10 or higher before sending to your real list.

Step 4 — Improve your email content

Spam filters score the content of your message. Common content problems:

• Subject line in ALL CAPS or with excessive exclamation marks (!!!) — avoid
• Spam trigger words in the subject: "Free", "Win", "Guaranteed", "Earn money", "Click here", "No obligation" — avoid or rephrase
• Emails that are image-only with no text — add real text content alongside images
• Too many links, especially to external domains — keep links minimal and relevant
• HTML with broken or invalid code — use a proper email builder or template
• Missing plain text version of the email — always include a plain text alternative
• No physical address or unsubscribe link (for newsletters) — both are legally required

Step 5 — Getting delisted from a blacklist

If your IP or domain appears on a blacklist, you must first fix the underlying cause (spam, compromised application, misconfiguration), then request removal:

1. Identify and fix the cause — check cPanel → Email → Track Delivery for bounced messages with blacklist codes, and review your website for compromised scripts or vulnerable contact forms.
2. Contact TPC Hosting support. We monitor IP blacklistings daily and can assist with delisting requests for shared hosting IPs.
3. For domain-specific blacklists, visit the blacklist's website directly — most provide a self-service delisting form (e.g. Spamhaus, Barracuda, SURBL).
4. After fixing the cause and requesting removal, delisting typically takes 24–72 hours.

Important: Requesting removal without fixing the cause will result in re-listing, and some blacklists will then require a waiting period before accepting a new removal request.

Step 6 — Warm up your sending reputation

If you are using a new domain or a new IP address, or if your reputation has been damaged, you need to rebuild it gradually:

• Start by sending small volumes — 20–50 emails per day — to your most engaged contacts (people who regularly open and reply to your emails)
• Gradually increase volume over 2–4 weeks
• Monitor open rates, bounce rates, and spam complaints throughout
• Avoid sending to your full list until your reputation is established

Sending large volumes from a cold domain immediately is the fastest way to get blacklisted and damage your long-term reputation.

Step 7 — Keep your mailing list clean

• Remove hard bounces immediately — these are invalid addresses and sending to them repeatedly harms your reputation
• Remove subscribers who have not opened your emails in 6 months or more
• Use double opt-in to ensure every subscriber intentionally signed up
• Never purchase, rent, or borrow email lists — this almost always results in blacklisting

Still getting blocked after all of the above?

Some scenarios require additional steps:

• Gmail / Outlook blocking — these providers have their own reputation systems. Register your domain with Google Postmaster Tools (https://postmaster.google.com) to see your domain reputation and spam rate as measured by Gmail.
• Sending large newsletters — shared hosting is not designed for bulk email. Consider using a dedicated email delivery service (e.g. Amazon SES, Mailgun, Brevo) for high-volume campaigns.
• Dedicated IP address — if your sending reputation is affected by other customers on the shared IP, a dedicated IP address isolates your traffic. Contact TPC Hosting support to discuss this option.

If you have completed all the steps above and emails are still being blocked, contact TPC Hosting support with the full bounce message or non-delivery report (NDR). This message contains the exact reason for the block and helps us assist you more effectively.