Is there a free alternative to Sublime?

Only your own Microsoft 365 or Google Workspace subscription. If you're on Business Premium you already own Defender for Office 365 Plan 1, turn on its anti-phishing and impersonation policies before spending anything else. Beyond that, nothing on this list has a real free tier — Abnormal and IRONSCALES are both paid from seat one.

Why do people switch away from Sublime?

Mainly two reasons: they want a fully hands-off tool and don't want anyone touching detection rules (go Abnormal), or they're already committed to an MSP that bundles IRONSCALES or Check Point Harmony. If neither applies, there's not much reason to leave — free for 100 mailboxes with transparent, tunable detection is hard to beat at this price.

Best-of guide

Best Sublime Security Alternatives

Sublime is our pick for payroll-diversion and BEC protection: free for your first 100 mailboxes, no MX change, and a detection engine you can actually read. It's not for everyone, above 100 mailboxes it's quote-only, and its best feature (tunable detection rules) only pays off if someone on your team will use it. Here's how the real alternatives differ.

01
Abnormal AI
Stops the 'update my direct deposit' email before payroll ever sees it
The fully hands-off premium option, worth it if you'd rather pay for accuracy than tune detection rules yourself
Contact the vendor for current pricing — Abnormal is premium, quote-only email security with no free tier, priced per mailbox on employee count plus paid onboarding (professional services commonly $5k-$25k+). Reported per-mailbox rates work out to a few dollars a month, so a 200-mailbox company should budget low five figures a year before services.8.0/10
02
IRONSCALES
Per-seat BEC and account-takeover protection priced for SMBs and the MSPs that serve them
The most straightforwardly SMB-priced dedicated option (tiers from about $3.89/user/month), especially if an MSP already manages your IT
Per-user monthly subscription across three tiers (Protect, Email Protect, Complete Protect). IRONSCALES doesn't publish seat prices on its own site, but third-party listings consistently put them around $3.89, $5.49-5.99, and $7.29 per user per month respectively, confirm your quote directly. Free trial, no free tier. An MSP partner program means your IT provider can often add it for you.7.7/10
03
Microsoft Defender for Office 365
The BEC baseline you may already be paying for inside Microsoft 365
Check this first if you're already paying for Microsoft 365 Business Premium, you may already own the baseline protection
Bundled into Microsoft 365 Business Premium ($22/user/mo), so many SMBs already own Plan 1. Standalone it's about $2/user/mo for Plan 1 and $5/user/mo for Plan 2 (which adds attack-simulation training plus automated investigation and response), billed annually. The real question isn't the price, it's whether you've turned on the anti-phishing and impersonation policies you already have.7.0/10

Questions buyers actually ask

Is there a free alternative to Sublime?: Only your own Microsoft 365 or Google Workspace subscription. If you're on Business Premium you already own Defender for Office 365 Plan 1, turn on its anti-phishing and impersonation policies before spending anything else. Beyond that, nothing on this list has a real free tier — Abnormal and IRONSCALES are both paid from seat one.
Why do people switch away from Sublime?: Mainly two reasons: they want a fully hands-off tool and don't want anyone touching detection rules (go Abnormal), or they're already committed to an MSP that bundles IRONSCALES or Check Point Harmony. If neither applies, there's not much reason to leave — free for 100 mailboxes with transparent, tunable detection is hard to beat at this price.