SMTP Error 252 - Cannot verify recipient, will attempt delivery. | Warmup Inbox

The short answer

Cannot verify recipient, will attempt delivery. Common cause: The server cannot confirm the address exists but will try anyway.

Quick fix

Usually fine — watch for a later bounce if the address turns out to be bad.

How to fix it

Usually fine — watch for a later bounce if the address turns out to be bad.

Related codes

211 System status or help reply.
214 Help reply.
220 Service ready.
221 Service closing transmission channel.
235 Authentication successful.
250 Requested action completed.

Most rejections come back to sender reputation.

Blocklists, auth failures, and policy blocks are what warmup prevents. Warm up your domain so your mail is trusted before you hit send.