Deliverability & HygieneEmail verification fundamentals before a campaign
An email marketer with permission to mail still needs a way to separate sendable rows from fixes, reviews, and holds. This is the operating checklist and the before-and-after process for that decision.
Deliverability & HygieneEmail verification fundamentals before a campaign
An email marketer with permission to mail still needs a way to separate sendable rows from fixes, reviews, and holds. This is the operating checklist and the before-and-after process for that decision.
Bulk Lists & FilesBulk email list verification before a send or CRM import
A file of addresses is not a send list and not a CRM update until each stored address has a branch: syntax, disposable, role, no usable mail server, catch-all, deliverable, or unknown.
Deliverability & HygieneReal-time email verification: should the signup form wait?
Wait on a signup email check only for broken syntax or a finished permanent reject inside a budget you set. A timeout or unknown result stays unresolved, and a confirmation link still has to prove the person controls the inbox.
Webhooks & APIsEmail verification API workflow for list jobs
A developer can put list verification into an application through the MailCheckup MCP server and webhooks. This is the run order, the failure states that are not an invalid address, and the credit-hold rules. It does not invent a REST base URL or a JSON schema.
Webhooks & APIsEmail verification webhooks: ack fast, apply once
A receiver design for developers who take MailCheckup list events on their own HTTPS URL: signature on the raw body, a stored evt_ id, an 8-second ack, and an action for all 10 published events.
MCP & AI AgentsEmail verification MCP: run a list without blocking the agent
An operator's sequence for the MailCheckup MCP server: read credits, load one list in chunks of 500, poll without blocking, leave unknown in place, and wait for the export email.
Protocols & SyntaxWhat an SMTP accept response proves about an email address
SMTP verification answers whether a mailbox server accepted a recipient during a check. This guide shows how to read that reply, and how to map accept, reject, defer, and timeout onto categories you can operate.
Protocols & SyntaxWhat an MX lookup can prove when a website already loads
A loading website proves that a web server answered. An MX lookup proves only the mail-exchange data DNS returned. This guide separates those facts from the assumptions people attach to them, including implicit MX, null MX, and an unreachable server.
Catch-All & DisposableCatch-all email results: what to keep, review, or suppress
When a list comes back catch-all, deleting the segment and marking it valid are both the wrong default. Acceptance proves domain policy. Your records decide keep, review, or suppress.
Catch-All & DisposableDisposable email detection policy: block, review, or allow by workflow
Disposable is a classification, not proof of fraud. Block it as the only recovery path, step up a trial, send the receipt, keep it off the newsletter, and allow a low-risk download. The cost sketch counts waste and legitimate users. Every volume in it is illustrative.
Billing & CreditsHow published plan rates and credits fit a list run
Match a list run to published credits, list caps, row caps, and the rate column. Unknown is free. A run does not start when available credits are zero.
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