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AhaSend SMTP errors tell you whether a connection, submission or recipient delivery failed; this reference helps you read the full reply and choose the next step.

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Where Did the Error Occur?

An error during your application’s connection to AhaSend is a submission problem. A reply recorded later in a delivery attempt came from the destination mail system. Fix the component that produced the reply: changing your SMTP password will not repair a nonexistent recipient mailbox. The three-digit SMTP reply gives a broad result. An enhanced code such as 5.1.1 adds detail. A 4xx reply is generally temporary; a 5xx reply is generally permanent for that attempt. Read the accompanying text and sender or recipient address. The SMTP standard and enhanced status code registry define these classes.

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What Do Common Codes Mean?

These are common SMTP meanings, not a promise that every server emits identical text.

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Why Does AhaSend Return a 556 Domain Error?

An AhaSend submission reply such as 556 Invalid account or domain or a reply saying the From domain is not allowed means the account, sender domain or credential’s domain access needs checking. Confirm that the From address uses a verified domain allowed by that credential. For a newly added or verified domain, use the refresh timing on domain setup. Do not infer that every 556 from every recipient server has this AhaSend-specific meaning. Keep the exact reply when reporting a problem.

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Why Does Port 465 Fail?

AhaSend does not support implicit TLS on port 465. Use STARTTLS on a supported port and authenticate after TLS, as described in SMTP settings. Do not disable certificate validation to get past a connection error. If your host blocks outbound SMTP, check its network policy or use the HTTPS API.

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Should I Retry a Failed Send?

Let AhaSend handle recipient delivery attempts after it accepts a message. A temporary delivery event is not a request for your app to send another copy. If the connection drops before you receive the final submission reply, the outcome can be uncertain; check the message log before retrying. SMTP has no equivalent of the REST API’s idempotency key.