MXToolbox Alternative · InbXr

MXToolbox looks up. InbXr reads.

Considering MXToolbox? Here's what it covers, what it misses, and where the Signal Engine reads the rest of your list.

What MXToolbox is

MXToolbox is the go-to reference for DNS lookups, MX records, blacklist checks, and SMTP diagnostics. If you need to look up a single domain's SPF record or check which blocklists a specific IP appears on, it's the cleanest free tool for the job.

What MXToolbox does well

DNS record inspection (A, MX, TXT, SPF, DMARC)
Multi-blacklist lookups against 100+ DNSBLs
SMTP path tracing
Free tier covers most one-off lookups

Signal coverage

InbXr reads 7 Inbox Signals across 100 weighted points. MXToolbox covers:

Signal 04 · Domain Reputation + Signal 06 · Authentication (partial, lookup-only)

20% of the 7-signal model

What MXToolbox doesn't read

Signal 01 · Bounce Exposure (no list verification)
Signal 02 · Engagement Trajectory (no ESP integration)
Signal 03 · Acquisition Quality (no cohort reading)
Signal 05 · Spam Trap Exposure (no list dormancy)
Signal 07 · Decay Velocity (no score history)
Continuous monitoring (you have to look things up manually)

MXToolbox answers a question you ask. InbXr answers questions you didn't know to ask. Asking 'is my domain blacklisted today' is useful. Knowing that your engagement trajectory is declining, your acquisition quality from one channel is dragging down your blended rate, and your DMARC policy is about to break Microsoft's 2025 enforcement window, is a different class of answer.

Side by side

Capability	MXToolbox	InbXr
DNS record lookup (on demand)	✓	✓
Blacklist lookup (on demand)	✓	✓
Continuous blacklist monitoring	×	✓
Continuous DMARC change detection	×	✓
List-level bounce prediction	×	✓
MPP-adjusted engagement reading	×	✓
Acquisition cohort analysis	×	✓
Pre-send status check (green/amber/red)	×	✓
Signal history and trajectory	×	✓

When MXToolbox is enough

If you need to diagnose a specific DNS or blacklist question once, MXToolbox gives you the fastest answer in the category.

When you need InbXr instead

If you want the tool to tell YOU when something changes, not wait for you to remember to check, you need continuous monitoring. InbXr watches all the DNS and blacklist data MXToolbox shows plus the 5 signals they don't cover.

Get your 7 Signal reading in 30 seconds

Type your sending domain. See the 2 signals the Signal Engine can read from DNS alone. Sign up to unlock the other 5.

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