MailerCheck
MailerCheck verifies individual email addresses and email lists, reports verification results, and tracks account credit balances.
Verdict
Common use cases
- Clean lead-gen CSVs before import
- Flag disposable emails at signup
- Audit subscriber lists before campaigns
- Triage support tickets by sender reputation
- Validate form submissions in real time
Integration
- Vendor
- MailerCheck
- Category
- other
- Auth
- API_KEY
- Tools
- 9
- Composio slug
mailercheck
Tools
- Create Verification List
Create a MailerCheck verification list by ingesting a name and email-address array. Creating a one-address list did not reduce the account credit balance during live probing. This action does not invoke the separate, credit-consuming Start
- Delete Verification Listdestructive
Permanently and irreversibly delete a MailerCheck verification list by ID. Use only when the caller explicitly intends to remove the list.
- Get Credit Balance
Return the current MailerCheck verification-credit balance. Use this before VERIFY_EMAIL or START_LIST_VERIFICATION when cost matters.
- Get Current Account
Return the connected MailerCheck user and account identity. Use this to confirm which user and account the API token represents.
- Get Verification List
Return one verification list, including its status, item count, verification timing, and aggregate result statistics.
- List Verification Lists
Return one page of verification lists for the connected MailerCheck account, with an opaque cursor when another provider-controlled page exists.
- List Verification Results
Return one page of email-level results for a verification list, optionally filtered by classification. The success envelope and pagination behavior are based on MailerCheck documentation and were not live-verified because producing results
- Start List Verification
Irreversibly start verification of every address in a MailerCheck list. A successful call spends one verification credit per address. Before calling, use GET_VERIFICATION_LIST to inspect the list count and GET_CREDIT_BALANCE to confirm the
- Verify Email
Consumes exactly one MailerCheck verification credit on every successful call. Synchronously verify one email address and return its classification; check GET_CREDIT_BALANCE first if cost matters.
Setup
Setup guide
- 11. In Switchy, open your workspace settings and navigate to the Integrations tab. 2. Click 'Add MCP' and search for MailerCheck. 3. You'll be prompted to paste an API key; generate one by logging into your MailerCheck dashboard, visiting API Settings, and creating a new token with verification permissions. 4. Paste the key into Switchy and click Connect. 5. To test, open any Project and type '@MailerCheck get my credit balance'—if the MCP returns a number, the connection is live. 6. To verify an address, type '@MailerCheck create a verification list with these emails: [paste addresses]' then '@MailerCheck start verification for list [ID]'. 7. Results appear in a few seconds for small lists; retrieve them with '@MailerCheck show results for list [ID]'.
What teammates see: by default, memories from MailerCheck are scoped to the Project (PROJECT visibility) - you can mark any memory PRIVATE or share it ORG-wide.
Works well with
Top models
Compatibility data appears once enough Projects have used this MCP together with a given model.
How Switchy teams use it
Starter prompts
Check Credit Balance
@MailerCheck show my current credit balance and tell me how many addresses I can verify.
Verify Single Address
@MailerCheck create a verification list with the email user@example.com, start verification, then show me the result classification.
Bulk List Verification
@MailerCheck create a verification list named 'Q1 leads' with these emails: [paste array], start verification, wait until complete, then summarize the deliverable, risky, and invalid counts.
Review Recent Lists
@MailerCheck list all my verification lists and show the name, status, and result summary for each.
Filter Risky Results
@MailerCheck retrieve results for list [ID] filtered to risky and invalid classifications, then format them as a CSV I can download.
Example outputs
Illustrative - representative of the model's voice and quality, not literal recordings.
@MailerCheck check my credit balance and show me the status of my three most recent verification lists
Your MailerCheck account has 4,732 verification credits remaining. Here are your three most recent lists: 'Q1 Newsletter Subscribers' (completed, 1,204 addresses, 89% deliverable), 'Webinar Registrants March' (in progress, 567 addresses, 42% verified so far), and 'Partner Outreach List' (created but not started, 320 addresses). The in-progress list should finish within the next 15 minutes.
This read-heavy example combines GET_CREDIT_BALANCE and LIST_VERIFICATION_LISTS to give budget-aware context before expensive operations. Useful when planning bulk verifications. Requires a valid API key with read permissions; credit balance reflects your actual account state at query time.
@MailerCheck create a new verification list called 'Conference Leads April' with these 50 email addresses, then start the verification immediately
Created verification list 'Conference Leads April' with 50 addresses (ID: vl_8x9k2m). Starting verification now—this will consume 50 credits from your balance of 4,732. Verification typically completes in 3–8 minutes for lists under 100 addresses. I'll monitor progress and can summarize results once the list status changes to 'completed'.
This write example chains CREATE_VERIFICATION_LIST and START_LIST_VERIFICATION to show the full workflow. Starting verification is irreversible and immediately deducts credits—one per address. Always confirm list size and credit cost before proceeding, especially with large imports.
@MailerCheck pull the detailed results from my 'Q1 Newsletter Subscribers' list and draft a summary email for our marketing team explaining which addresses we should remove
Retrieved 1,204 results from 'Q1 Newsletter Subscribers'. Found 132 addresses (11%) flagged as undeliverable: 78 invalid domains, 31 role-based addresses (info@, support@), 18 disposable email providers, and 5 syntax errors. Drafted summary: 'Team—our Q1 list verification identified 132 addresses to remove before the next campaign. Cleaning these will improve our sender reputation and reduce bounce rates. The invalid domains (78) are the largest segment; recommend scrubbing similar patterns from future imports. Full CSV export attached.' This prevents roughly 11% of your sends from bouncing.
This synthesis example uses LIST_VERIFICATION_RESULTS to fetch granular data, then applies AI reasoning to categorize issues and draft stakeholder communication. Demonstrates how verification insights translate into actionable list hygiene. Results reflect the specific list queried; your data will differ.
Use-case deep-dives
When MailerCheck wins for cold-email list cleaning
A 6-person sales team scraping 2,000 leads a week from LinkedIn and conference lists needs to verify deliverability before burning their domain reputation. MailerCheck is the right call here: create a verification list from the scraped CSV, check your credit balance, start the batch verification, then pull results filtered by 'deliverable' to feed your outbound tool. The MCP's 9 tools cover the full verify-and-export loop without leaving Switchy. The threshold: if you're verifying under 500 addresses a month, a one-off web upload is faster than wiring the MCP. Above that volume, the automation pays back in the first sprint. Wire this MCP when your list-building cadence is weekly or faster and you need programmatic access to results.
When MailerCheck handles newsletter-subscriber cleanup
A 3-person marketing team running a 40,000-subscriber newsletter sees bounce rates creeping above 3 percent and wants to prune invalid addresses before their ESP flags them. MailerCheck fits: export the subscriber CSV, create a verification list, start verification, then pull the 'invalid' and 'risky' results to suppress in the ESP. The MCP's list-management tools let you track multiple cleanup runs and compare result stats over time without switching contexts. The trade-off: MailerCheck charges per verification, so if your list churn is under 200 new signups a month, manual spot-checks are cheaper. Use this MCP when you're adding 1,000-plus subscribers a quarter and need repeatable, credit-tracked verification inside your workspace.
When MailerCheck isn't the tool for CRM contact validation
A 5-person customer-success team wants to verify 8,000 CRM contacts to improve email-campaign targeting and reduce support-ticket noise from bounced messages. MailerCheck can technically do this—create a list, verify, export results—but it's borderline. The MCP has no native CRM integration, so you're exporting CSV, verifying in MailerCheck, then manually re-importing the classification tags. If your CRM already has a built-in verification partner (HubSpot, Salesforce), use that instead; the round-trip through MailerCheck burns credits without saving time. Choose this MCP only if your CRM lacks verification, you're running the audit once a quarter, and you need the credit-balance visibility to budget the spend. For ongoing, per-contact validation, a CRM-native tool wins.
Frequently asked
What does the MailerCheck MCP do in Switchy?
It verifies email addresses in bulk by checking deliverability, syntax, and domain health. You create lists of addresses, start verification runs, and retrieve results showing which emails are valid, risky, or invalid. Switchy agents can check your credit balance, manage lists, and filter results by classification—all without leaving the workspace.
Do I need a paid MailerCheck account to use this MCP?
Yes. You need an active MailerCheck account with verification credits and an API key. Each verification consumes one credit per address, so check your balance with the Get Credit Balance tool before running large lists. The MCP won't create credits; it only spends what you already own.
Can the MCP verify a single email address on demand?
No. MailerCheck's API requires you to create a list first, even for one address. During testing, single-address lists didn't deduct credits, but production runs will. If you need instant one-off checks, use MailerCheck's web dashboard instead—this MCP is built for batch workflows.
How does this compare to calling MailerCheck's API directly?
The MCP wraps the same endpoints but lets Switchy agents orchestrate multi-step workflows—create list, verify, filter results, delete—in natural language. You skip writing pagination logic or credential management. Trade-off: you can't access beta endpoints or undocumented features until we add them.
Who on the team should connect the MailerCheck account?
Whoever owns the MailerCheck subscription and API key. That person's credit balance applies to all verifications triggered through Switchy. If multiple people need access, share one API key or rotate keys when the owner changes—MailerCheck doesn't support team-level tokens.