# Inbound spam filtering for hosting providers

URL: https://iblockspam.com/solutions/hosting-providers
Last updated: 2026-10-09

> Add per-domain inbound spam filtering to your hosting plans. Works with cPanel/WHM, with partner terms, including pricing, agreed individually.

Offer your customers business-grade inbound filtering in front of the mail servers you already run. Priced per domain, with partner terms, including pricing, agreed individually.

## Why hosts add inbound filtering

Shared and reseller hosting customers expect email to just work. When it doesn't, the ticket lands with you: spam floods, phishing that gets through, a customer who blames the server. Filtering inbound mail before it reaches your servers reduces load on your mail stack and gives customers controls they can manage themselves.

iBlockSpam is priced per domain, which fits how hosting is sold. A customer with one mailbox and a customer with forty pay the same for a domain.

## What your customers get

- **Inbound filtering** for spam, viruses, malware, phishing and spoofing at the MX level.
- **Personal quarantine** for every mailbox, with digests hourly, daily, on a chosen weekday or a custom schedule.
- **Shared quarantine** for the domain admin.
- **Approved and blocked sender lists**, with optional sender verification.
- **Advanced settings:** geographic filters, attachment-type filters, a Microsoft Office macro filter and custom domain rules.
- **Outage spooling:** if the destination server is down, mail is held for up to 5 days and delivered when it's back. Useful during maintenance windows and migrations.
- **30 days of message history** for "did it arrive?" questions.
- **Outbound relay** with DKIM signing and outbound filtering, 500 messages per domain per month.

## What hosting partners get

| | Details |
|---|---|
| Commercial model | Partner terms, including pricing, agreed individually |
| Pricing basis | Per domain; unlimited mailboxes (count, not message volume) and unlimited domain aliases |
| Monitoring | Drift alerts for MX, SPF and DMARC (weekly on Protect, daily on Plus) |
| Setup | Guided setup with before/after DNS comparison and rollback steps |
| Inquiries | [Contact us](https://iblockspam.com/contact); program details confirmed per partner ([how partnering works](https://iblockspam.com/partners)) |

## Fitting it into cPanel/WHM

### Routing

The domain's MX records point to our filtering servers. Your server stops being the public MX but still delivers mail to local mailboxes. In cPanel, that usually means reviewing the domain's email routing so the server treats itself as the final destination even though it isn't the MX. Don't apply a blanket setting across all accounts without checking each domain's topology, especially for:

- Domains with split delivery or remote mail elsewhere
- Aliases, forwarders and catch-all addresses
- Domains that receive over IPv6
- Accounts with an existing secondary MX

Our [cPanel/WHM guide](https://iblockspam.com/platforms/cpanel-whm) walks through these cases.

### Accepting filtered mail

Once filtering is live, your server receives mail from the filtering service rather than directly from senders. Make sure firewall rules, rate limits and local spam scoring don't penalize that traffic. Senders may also still try your server directly using old MX data or hard-coded hosts; decide whether to restrict direct delivery after you've tested.

## Limits

| Limit | Per domain |
|---|---|
| Inbound messages included | 100,000 per month |
| Maximum inbound message size | 400 MB |
| Outbound relay messages included | 500 per month |
| Outage spooling | Up to 5 days |
| Message history | 30 days |

Mail is processed in the United States. Read [security and data handling](https://iblockspam.com/security) before offering it in regions with specific requirements.

## Before you roll out

1. Run your test domains through the [Email Health Check](https://iblockspam.com/tools/email-health-check) to see current MX, SPF and DMARC.
2. Pilot with a few domains you control and verify delivery end to end.
3. Read [how to switch filters without losing email](https://iblockspam.com/migrate) if customers already use another service.
4. [Contact us](https://iblockspam.com/contact) to agree partner terms.

## Frequently asked questions

### Does this replace SpamAssassin or our server-side filtering?

It sits in front of it. Mail is filtered on our infrastructure before it reaches your server, so less junk arrives at all. You can keep server-side filtering as a second layer, but review its settings so it doesn't fight with decisions already made upstream, and make sure your server accepts mail from the filtering service.

### How does it work with cPanel/WHM?

The domain's MX records point to our filtering servers, and the domain's mail exchanger setting in cPanel is set so the server still accepts and delivers mail locally. The correct setting depends on your routing, so our cPanel/WHM guide covers local delivery, aliases and catch-all cases.

### What are the partner terms?

Partner terms, including pricing, are agreed individually with each hosting provider, along with billing, provisioning and the support model. Contact us with the approximate number of domains and your control panel setup.

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Source: iBlockSpam, https://iblockspam.com/solutions/hosting-providers (this is a Markdown copy; the HTML page is canonical). Quote with attribution and a link. Site index for AI assistants: https://iblockspam.com/llms.txt