The short answer
Mimecast suits organizations that want one vendor for advanced threat protection, continuity, archiving and integrations, and are comfortable buying through a sales quote. iBlockSpam suits small and mid-sized businesses that want straightforward MX filtering with a flat, published per-domain price, unlimited mailboxes, per-user quarantine digests and free DNS tools.
Competitor details below were checked on Mimecast's own pages in October 2026.
Side by side
| Item | Mimecast | iBlockSpam |
|---|---|---|
| Pricing model | Plans by quote | Per domain, unlimited mailboxes (mailbox count, not message volume) |
| Published price | None on the plan pages ("Contact for pricing") | Protect $12 per domain/month billed annually ($144/year) or $15 month-to-month; Protect Plus $19 annually or $24 monthly. Beta pricing, USD, excluding tax |
| Minimum | Not published | 1 domain |
| Trial or guarantee | 30-day proof of value via API for Microsoft 365, no payment details | No free trial; 30-day money-back guarantee on a domain's first annual subscription |
| Continuity if your server is down | Email continuity with the MX-based Cloud Gateway; duration not stated on the pages we checked | Mail spooled for up to 5 days, then delivered |
| Quarantine and digests | Held-message digests to end users; frequency set by the administrator | Personal quarantine for every user; digests hourly, daily, on a chosen weekday or custom; shared admin quarantine |
| Sandboxing and link analysis | Attachment sandboxing and on-click URL analysis in the Critical plan | Neither |
| Archiving | Mimecast Cloud Archive | 30-day message history only |
| Setup method | MX-based gateway or API-based deployment | MX change plus platform steps, with a guided setup wizard and rollback steps |
| Free tools | SPF and other DNS record checkers (DMARC Analyzer) | Email Health Check, MX, SPF, DKIM, DMARC, blacklist, PTR, MTA-STS, BIMI, header analyzer, SPF and DMARC generators |
| Contract notes | Through sales ("Get a Quote") | Annual or month-to-month; cancel any time in the billing portal, effective at period end |
What it costs at 10 and 50 mailboxes
Assumptions: one domain, published prices only, USD, excluding tax.
| Item | 10 mailboxes | 50 mailboxes |
|---|---|---|
| Mimecast | Quote only | Quote only |
| iBlockSpam Protect, annual | $12/month ($144/year) | $12/month ($144/year) |
| iBlockSpam Protect Plus, annual | $19/month ($228/year) | $19/month ($228/year) |
| iBlockSpam Protect, month-to-month | $15/month | $15/month |
Mimecast doesn't publish a price on its plan pages, so we can't show a fair number here, and we won't guess. When you get a quote, compare it against what you'd actually use. A Mimecast plan includes sandboxing, click-time link analysis and other protections that iBlockSpam doesn't have.
When Mimecast is the better choice
- You need advanced threat protection. Mimecast's Critical plan lists attachment sandboxing, on-click URL analysis, QR code protection, browser isolation and BEC protection. iBlockSpam offers none of these.
- You need archiving. Mimecast sells a cloud archive for retention and eDiscovery. iBlockSpam keeps 30 days of history only.
- You want users to keep working during an outage. Mimecast's Cloud Gateway includes email continuity. iBlockSpam holds mail for up to 5 days but doesn't give users an emergency mailbox.
- You want a no-MX-change evaluation. Mimecast's 30-day proof of value connects to Microsoft 365 by API.
- You're a larger organization with a security team, integration needs and a procurement process built around quotes.
When iBlockSpam is the better choice
- You want a price you can read now. Prices and per-domain limits are on the pricing page, with no quote step.
- You have many mailboxes or aliases. Unlimited mailboxes and domain aliases per domain, with 100,000 inbound messages a month included.
- You want per-user quarantine without configuration work. Every user gets a personal quarantine and digests as often as hourly.
- You want filtering only, not a platform. If Microsoft 365 or Google Workspace already covers the rest of your security, a focused MX filter in front of it can be enough. iBlockSpam works with Microsoft 365, Google Workspace, cPanel/WHM, Exchange and other servers.
- You want free, ungated tools. Our tools need no sign-up, and the Email Health Check checks MX, SPF, DKIM and DMARC in one pass.
- You want a refund window. A domain's first annual subscription has a 30-day money-back guarantee; see the refund policy.
If you're weighing an MX gateway against API-based tools in general, our guide to secure email gateways vs API email security sets out the trade-offs.
How to switch from Mimecast
- Decide what replaces the parts iBlockSpam doesn't cover, such as archiving, continuity or link protection. Microsoft Defender for Office 365 may already cover some of this; see Defender vs a gateway.
- Export your permitted and blocked sender lists so you can recreate them.
- Save a copy of your current DNS with the Email Health Check and lower your MX TTL a day or two ahead.
- Add your domain in iBlockSpam and follow the guided setup for your platform, including any inbound connector changes in Microsoft 365.
- Change MX, test, and check the delivery path in the Email Header Analyzer.
- Keep Mimecast routing in place until the old TTL has passed and no new traffic arrives there. If you locked your Microsoft 365 tenant to accept mail only from Mimecast, update that restriction as part of the cutover.
Our migration plan covers each step and the rollback, and the guide to switching spam filter providers explains the common pitfalls.
Mimecast is a trademark of its owner; iBlockSpam is not affiliated with Mimecast.
Sources
Checked October 2026.
- Mimecast: plans (Critical plan protections, "Contact for pricing")
- Mimecast: email security (MX-based and API-based deployment, continuity)
- Mimecast: proof of value (30 days, API, no MX changes, no payment details)
- Mimecast: email archive
- Mimecast support: configuring digest set emails
- Mimecast: SPF record check
Frequently asked questions
Does Mimecast publish its prices?
Not on the plan pages we checked in October 2026. Mimecast's plans page shows its Critical plan as "Contact for pricing" and the Advanced plan as "Custom pricing available". iBlockSpam publishes per-domain prices: Protect is $12 per domain per month billed annually or $15 month-to-month.
Can I test Mimecast without changing my MX records?
Yes, for Microsoft 365. Mimecast's proof-of-value page offers a 30-day assessment that connects by API, with no MX changes and no payment details. iBlockSpam works at the MX level, so there's no API-only test; instead, our free tools check your DNS and a first annual subscription has a 30-day money-back guarantee.
Does iBlockSpam rewrite links or check them at click time like Mimecast?
No. iBlockSpam doesn't rewrite links or analyze them at click time, and it doesn't sandbox attachments. It filters spam, viruses, malware, phishing and spoofing before delivery. If click-time link protection matters to you, Mimecast includes on-click URL analysis in its Critical plan.
Can I replace Mimecast's archive with iBlockSpam?
No. iBlockSpam keeps 30 days of message history, which is useful for tracing a missing message but isn't an archive for compliance or eDiscovery. If you rely on Mimecast's Cloud Archive, keep an archiving service in place or plan a separate one before you switch.
Related guides
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