Email spam filtering is automated, complex, and reputation-based.
This guide explains why legitimate emails are flagged as spam, what factors matter most, and what you can realistically do to improve deliverability when sending email from A7 Host.
1. Important Reality Check
Email delivery is never guaranteed.
Even when:
- Servers are working correctly
- Settings are configured properly
- No errors are shown
Receiving mail providers (Gmail, Outlook, Yahoo, etc.) still decide where your email lands.
A7 Host provides the sending infrastructure, but receiving servers make the final decision.
2. How Spam Filtering Actually Works
Spam filters do not rely on one rule.
They evaluate multiple signals at the same time, including:
- Sender authentication (SPF, DKIM, DMARC)
- Domain reputation
- IP reputation
- Email content
- Sending behavior
- Recipient engagement
- Historical sending patterns
One weak signal can be enough to trigger spam placement.
3. Missing or Incorrect Email Authentication (Top Reason)
SPF Failure
If your domain does not authorize A7 Host mail servers:
- Messages fail SPF checks
- Emails are marked suspicious
Fix:
Add a correct SPF record including include:a7host.com.
DKIM Failure
If DKIM is missing or broken:
- Emails cannot be verified
- Integrity cannot be confirmed
Fix:
Enable DKIM and ensure the DNS record is published correctly.
DMARC Not Configured
Without DMARC:
- Receiving servers have no clear policy
- Domain trust is lower
Fix:
Add a DMARC record (start with p=none).
4. Domain Reputation (New Domains Are Treated With Caution)
New domains = low trust
If your domain is:
- Newly registered
- Newly sending email
- Previously unused for email
It has no reputation.
Spam filters are cautious by default.
What this means in practice
- First emails may go to spam
- Small volumes are expected
- Reputation builds over time
This is normal behavior, not a server issue.
5. Sending Behavior (How You Send Matters)
Sudden volume spikes
Sending:
- 50+ emails suddenly
- Bulk emails from a new mailbox
- Identical emails to many recipients
Triggers spam filters immediately.
Best practice
- Start small
- Send gradually
- Avoid mass sending from hosting email
Shared hosting email is not designed for bulk marketing.
6. Email Content Triggers
Spam filters scan email content aggressively.
Common red flags
- Excessive links
- All-caps subject lines
- Spam keywords (“free”, “urgent”, “act now”)
- Poor formatting
- Large images with little text
- Short or empty messages
HTML formatting issues
- Broken HTML
- Copied email templates
- External tracking pixels
All increase spam likelihood.
7. Recipient Behavior (Out of Your Control)
Receiving providers track how recipients interact:
- Emails opened?
- Emails deleted without reading?
- Emails marked as spam?
- Replies sent?
Negative engagement lowers reputation even if everything is configured correctly.
8. Shared IP Reputation (Reality of Shared Hosting)
On shared hosting:
- Multiple customers send mail from shared infrastructure
- Providers isolate accounts, but IP reputation is shared
A7 Host actively monitors abuse, but reputation is still influenced collectively.
This is why:
- Bulk mailing is restricted
- Abuse accounts are terminated quickly
9. Blacklists (Less Common Than People Think)
Most spam issues are not caused by blacklists.
Blacklisting usually occurs due to:
- Malware
- Spam campaigns
- Compromised accounts
If blacklisted:
- Support will assist at infrastructure level
- Cleanup and reputation recovery take time
10. Common Misconceptions
- “My email server is broken”
- “Hosting provider is blocking emails”
- “Gmail is wrong”
- “It worked before, so it should work now”
Spam filtering is dynamic, not static.
11. What You Can Control (Action Plan)
Must-do checklist
☐ SPF configured correctly
☐ DKIM enabled and passing
☐ DMARC added (monitoring mode)
☐ Strong passwords
☐ Clean email content
☐ Gradual sending behavior
Strongly recommended
- Use IMAP (not POP3)
- Use professional signatures
- Avoid forwarding chains
- Avoid email blasts from hosting mail
12. When Hosting Email Is Not the Right Tool
Hosting email is designed for:
- Personal correspondence
- Business communication
- Low-volume transactional email
It is not designed for:
- Email marketing
- Newsletters
- Cold outreach
- Campaign tracking
For those use cases, use a dedicated email service provider.
13. How to Test Deliverability Correctly
Send a test email to:
- Gmail
- Outlook
- Yahoo
In Gmail:
- Open email
- Click “Show original”
- Check:
- SPF: PASS
- DKIM: PASS
- DMARC: PASS
Failures here indicate configuration issues.
14. When to Contact Support
Contact support if:
- SPF/DKIM/DMARC fails after 24 hours
- Email is rejected (bounced), not just spam
- Authentication errors appear
- Delivery suddenly stops completely
Support portal:
https://www.a7host.com/billing
15. Final Summary
Emails go to spam because trust is earned, not granted.
Correct configuration is required, but not sufficient on its own.
Reputation, behavior, and content all matter.
Once you understand this, deliverability becomes predictable—and fixable.
