Best deliverability monitoring tools
Bounce and complaint rates tell you a problem happened. A monitoring tool tells you where a message actually landed before you find out from a dead campaign.
GlockApps wins for a team that wants dedicated inbox-placement testing across many providers in one dashboard; Google Postmaster Tools wins as a free companion for the Gmail slice of the list specifically.
The short answer
- GlockApps' Essential plan starts at $59/mo and includes inbox-placement tests across 70-plus seed addresses spanning Gmail, Outlook, Yahoo and corporate filters.
- Google Postmaster Tools is free and shows domain reputation, IP reputation and spam-rate data, but only for mail sent to Gmail addresses, not the rest of a mixed B2B list.
- A monitoring tool answers a different question than a warmup tool: warmup tries to build reputation before you send at volume; monitoring tells you what happened to a message you already sent.
- None of these tools fix a deliverability problem by themselves. They diagnose it; fixing it usually means slowing send volume, improving list hygiene, or moving a burned domain out of rotation.
How we compared these
We compared tools on what they test (inbox placement across which providers, spam-score analysis, reputation monitoring), starting price, and whether the tool is free or standalone versus bundled into a broader sending platform. Facts checked on vendor pricing pages, September 2026.
Deliverability monitoring comparison
| Tool | Starting price | What it tests | Provider coverage | Best for | Not for |
|---|---|---|---|---|---|
| GlockApps | $59/mo Essential (annual billing), unlimited spam tests | Inbox placement, spam-score analysis, blacklist monitoring | 70+ seed addresses across Gmail, Outlook, Yahoo, corporate filters | A team that wants one dashboard covering most major providers | A team that only cares about Gmail and does not want a paid tool |
| Google Postmaster Tools | Free | Domain reputation, IP reputation, spam rate, feedback loop data | Gmail only | Any sender, as a free baseline check on the largest single provider | A full picture across Outlook, Yahoo or corporate spam filters |
| Mailreach | $19.50/mailbox/mo, All-In-One plan (warmup plus 20 spam-test credits) | Warmup plus deliverability monitoring in one subscription | Multiple major providers via its spam-tester credits | A team that wants warmup and monitoring from a single vendor | A team that already has a warmup tool and only wants monitoring |
Figures checked on vendor pricing pages, September 2026, including mailreach.co/pricing.
The field, ranked
1. GlockApps
Dedicated inbox-placement testing across dozens of real seed addresses, with a spam-score breakdown per test. The clearest single-purpose tool in this category. Best for: a team running sustained cold outbound that wants a weekly placement check. Not for: a team on a tight budget that only sends occasionally.
2. Google Postmaster Tools
Free and directly from Gmail, showing domain and IP reputation data no third-party tool can see as accurately. Best for: any sender, as a baseline check that costs nothing. Not for: full coverage; it says nothing about Outlook or Yahoo placement.
3. Mailreach
Combines warmup and monitoring in one $19.50/mailbox/mo subscription, useful for a team that wants fewer vendors rather than the deepest tool in either category alone. Best for: a smaller team consolidating tools. Not for: a team that wants the most detailed placement data available; a dedicated tool usually goes deeper.
When none of these is the answer
A team sending a few dozen relationship emails a week from an established company domain does not need deliverability monitoring. The volume is too low to create a reputation problem worth diagnosing with a dedicated tool. Monitoring earns its place once sending moves to a secondary domain and sender pool at real cold-outbound volume, where a single bad domain can silently drag down replies for weeks before anyone notices.
Questions
- What is the difference between deliverability monitoring and email warmup?
- Warmup builds sending reputation over time by having a mailbox exchange real-looking mail with a network of other inboxes. Monitoring is a diagnostic check that tells you where a specific send actually landed, inbox, promotions or spam, across different providers. Most teams need both, not one instead of the other.
- Is Google Postmaster Tools enough on its own?
- It is free and shows Gmail-specific data, spam rate, domain reputation and IP reputation, which is useful because Gmail is often the biggest slice of a B2B list. It only covers Gmail, though, so it misses problems specific to Outlook, Yahoo or corporate spam filters that a broader seed-list tool would catch.
- How often should deliverability be checked during an active campaign?
- Weekly at minimum during sustained sending, and immediately after any change to sending volume, a new domain joining the pool, or a spike in bounces or complaints, since those are the events most likely to have moved a domain's reputation.
- Does SalesCrew include deliverability monitoring?
- Disclosure: SalesCrew is our product. It tracks bounce and complaint rates per mailbox and moves a mailbox to suppression automatically when they spike, but it does not run inbox-placement seed tests the way a dedicated tool like GlockApps does. The two are complementary.