Zix and AppRiver alternative: an honest comparison

The short answer

OpenText Core Email Threat Protection suits businesses, especially on Microsoft 365, whose MSP already runs OpenText's stack and who want filtering, attachment sandboxing, time-of-click link checks, message retraction, encryption and a continuity mailbox from one vendor. iBlockSpam suits businesses that want inbound filtering they can buy themselves, with a flat published per-domain price, unlimited mailboxes, flexible digests, free DNS tools and a 30-day money-back guarantee.

Competitor details below were checked on OpenText's own pages in October 2026.

Side by side

What it costs at 10 and 50 mailboxes

Assumptions: one domain, published prices only, USD, excluding tax.

If an MSP bundles OpenText email security with Microsoft 365, backup or endpoint protection, compare the whole bundle, not just the filtering line.

When OpenText Email Threat Protection is the better choice

• Your MSP already runs it with other OpenText products and handles quarantine and support for you.
• You want attachment sandboxing and time-of-click link checks. OpenText lists both. iBlockSpam does neither.
• You need encryption or a continuity mailbox. Email Encryption and Email Continuity, with 30 days of stored messages during an outage, come from the same vendor.
• You want message retraction in Microsoft 365 or filtering of internal mail between your own users.
• You want 24/7 threat analyst support, which OpenText lists for the product.

When iBlockSpam is the better choice

• You don't have an MSP, or want to own your filtering directly. You can sign up and pay per domain without a partner agreement.
• You want prices you can read. Prices and per-domain limits are on the pricing page.
• You have many users, shared mailboxes or aliases. One price per domain covers unlimited mailboxes and domain aliases, with 100,000 inbound messages a month.
• You want each user to choose their digest schedule. Digests can run hourly, daily, on a chosen weekday or custom.
• You aren't on Microsoft 365. Guided setup also covers Google Workspace, cPanel/WHM and Exchange.
• You want DNS drift alerts and free tools. Domain monitoring is included, and our tools need no sign-up.

How to switch from Zix, AppRiver or OpenText

1. If an MSP manages OpenText for you, tell them your plan and agree a cutover date and notice period.
2. Export allow and block lists, and decide what replaces Email Encryption or Email Continuity if you use them.
3. Save your current DNS with the Email Health Check and lower the MX TTL a day or two ahead.
4. Add your domain in iBlockSpam and follow the guided setup for your platform, such as the Microsoft 365 inbound connector with Enhanced Filtering for Connectors.
5. Update any connector or firewall rule that only accepts inbound mail from OpenText, and move your outbound relay if it runs through OpenText.
6. Change MX, test with the Email Header Analyzer, and keep the old service active until the old TTL has passed and no new mail arrives there.

Our migration plan covers each step and the rollback.

OpenText, Zix, AppRiver and Webroot are trademarks of their owner; iBlockSpam is not affiliated with OpenText.

Sources

Checked October 2026.

• OpenText Cybersecurity: brand acquisition timeline and product naming (AppRiver 2019, Zix 2021, Webroot product renames)
• OpenText Cybersecurity: AppRiver is now OpenText Cybersecurity
• OpenText: Core Email Threat Protection (inbound, outbound and internal filtering, sandbox, time-of-click links, retraction, quarantine reports, 24/7 analyst support)
• OpenText: Core Email Continuity (spooling at the filter, 30 days of stored messages, requires Core Email Threat Protection or Core Advanced Email Threat Protection)
• OpenText: email security portfolio (encryption, message privacy, continuity, awareness training)
• OpenText: MSP solutions (monthly billing, no long-term commitments)