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Guide BillionMail Deliverability: Test Your Email and Fix Spam Problems - Printable Version

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BillionMail Deliverability: Test Your Email and Fix Spam Problems - JAY - 10-21-2026

BillionMail deliverability: test your email and fix spam problems

Your newsletter sends, but does it reach the inbox? This guide shows how to measure it with a free email tester, what each result means, and how we took a fresh BillionMail server from 89/100 (B) to 95/100 (A).

Step 1: Get a test address
Open the free SEOStackTools Email Tester (no signup) and click Get My Test Address. You get a unique address like [email protected].

[Image: attachment.php?aid=420]

Step 2: Send a real test from BillionMail
Test the real thing: your server, your sender, your template. Open your task in Email Marketing (or create one), paste the address into Test email and click Send test mail. Then go back to the tester and click Check My Score. Give it a minute if it says nothing has arrived yet.

Tip: copy-paste the address. We typed it once and an extra letter slipped in, so the test went nowhere.

Step 3: Read the report
You get a score out of 100, a grade, and a "What To Fix First" list, sorted by importance. Under the technical details:
  • Authentication: SPF, DKIM and DMARC. All three should pass.
  • Content & Spam Signals: subject, spam words, HTML and plain text, links, unsubscribe header, attachments.
  • Technical: Message-ID, Date, encoding, blacklists and reverse DNS (PTR).
  • Email Headers: the delivery path and the IP your mail really left from.

Our first result: 89/100, grade B
SPF, DKIM and DMARC passed and the IP was on no blacklists. The tester flagged four things:
  1. Spam trigger words in the content.
  2. HTML only, no plain-text version.
  3. Reverse DNS (PTR) missing. This was the only real error.
  4. No List-Unsubscribe header.

How we fixed each one
Reverse DNS (PTR). Only your VPS provider can set it. We opened a ticket asking for IP -> bm.ourdomain.com; it was done within a day. Check:
Code:
dig +short -x YOUR_SERVER_IP
The answer must be your mail server name, and that name's A record must point back to the same IP. In BillionMail, Domain > DNS Records then shows all six checks green.

Spam trigger words. We rewrote the template in plain language: no "free", no "marketing platform", no "campaign", and a clear line explaining why the reader gets the email. The warning disappeared.

Plain-text version. Emails with both an HTML and a plain-text part look more legitimate. BillionMail 4.9.0's template editor only accepts HTML, so this can't be fixed from the dashboard yet. It's a small deduction; we left it.

List-Unsubscribe header. Gmail and Yahoo require one-click unsubscribe for bulk senders. Keep Unsubscribe link switched on in every task. Test sends may not include the header, so also test a real send: add the tester address to a small test group and send the task to that group.

After the fixes: 95/100, grade A
[Image: attachment.php?aid=421]
Zero errors, 12 checks passed. That's a properly configured server.

Troubleshooting checklist
  • Mail never arrives anywhere: outgoing port 25 is blocked. Test with nc -vz -w 5 gmail-smtp-in.l.google.com 25. Ask your provider to open it, or use an SMTP relay under SMTP.
  • SPF fails: the sending IP isn't in your SPF record, or you have two SPF records for the same name.
  • DKIM fails although the record exists: check s= in the DKIM-Signature header of the received mail. That's the selector in use; add a record for exactly that selector. Our mail was signed with a selector called short, so we added short._domainkey too.
  • DMARC fails: SPF or DKIM must pass and match the domain in your From address. Send from an address on the domain you set up.
  • "HELO localhost" or a strange server name in the headers: set myhostname in Postfix. See BillionMail SSL certificate and hostname fix.
  • IP on a blacklist: find out why (often a previous owner of the IP), fix it, then follow that list's delisting steps.
  • Mail stuck in the queue: Settings > Send Queue shows the delay reason for each message.
  • Everything passes but Gmail still puts it in spam: that's reputation. Warm up: send to small, engaged groups first and grow over a few weeks. Keep the IP Warmup switch on. Remove bounced addresses.
  • Cloudflare: mail records must be DNS only (grey cloud).

Make testing a habit
Run a test after every change to DNS, your server or your template, and before every big send. It takes a minute and catches problems before your subscribers (and Gmail) do.

Stuck? Post in aaPanel BillionMail Support with your score, the failing checks and any error message.

More BillionMail how-to guides
Tested on BillionMail 4.9.0 through aaPanel, October 2026. Sources: SEOStackTools Email Tester · Google: email sender guidelines · RFC 8058: one-click unsubscribe.