SMTP Error 441

Is SMTP Error 441 a real SMTP code?

No. The Simple Mail Transfer Protocol (RFC 5321 §4.2.3) defines only a handful of 4yz Transient Negative Completion reply codes — 421, 450, 451, 452, 455 and a few auth-related ones. There is no reply code 441 in the standard. A mail server will never legitimately answer a command with a 3-digit 441.

So when you see "441," it's almost always one of two different things wearing the same label:

1. The enhanced status code 4.4.1 — a RFC 3463 Delivery Status Notification code, not a reply code. The dot gets dropped in logs and tooling, leaving "441." This is the common case.
2. A provider-specific 441 — most notably AuthSMTP, which uses 441 to mean "Account is at / over data quota."

Identifying which one you have is the whole job. Look at the raw log line.

What does the 4.4.1 "No answer from host" version mean?

If your logs show dsn=4.4.1, status=4.4.1, or a deferred message citing 4.4.1, this is RFC 3463's X.4.1: "No answer from host." Per the RFC: "The outbound connection attempt was not answered, because either the remote system was busy, or was unable to take a call. This is useful only as a persistent transient error."

In plain terms: your server tried to open an SMTP connection to the recipient's mail host and got no response. It's the X.4 (Network and Routing) class — a connectivity problem, not a rejection of your message content. Your MTA will keep retrying on its normal schedule.

How do I fix a 4.4.1 / deferred error?

• Wait — it's transient by design. Most 4.4.1 deferrals clear on their own within minutes to a few hours as the recipient host comes back or load drops. Your queue retries automatically; you usually don't need to resend.
• Confirm the recipient's MX is resolvable and reachable. Run dig MX recipientdomain.com, then test the connection: telnet <mx-host> 25 (or openssl s_client -starttls smtp -connect <mx-host>:25 for a TLS-aware check on the same relay port). No banner = the remote side is down or filtering you.
• Check that your outbound port 25 isn't blocked. Residential and many cloud networks block outbound 25, which produces "no answer from host" symptoms. Relay through a smarthost/submission service instead of delivering direct-to-MX.
• Verify your sending IP isn't being silently dropped. Some receivers tarpit or refuse connections from IPs with poor reputation. Check blocklists and ensure forward/reverse DNS (PTR) match.
• If it persists for many hours, the recipient domain's mail is genuinely down — contact the recipient through another channel.

What does the AuthSMTP version mean?

If you relay through AuthSMTP and see 441, it means "Account is at / over data quota." Each AuthSMTP plan has a monthly message and data allowance, and a single 1 MB attachment can consume 1–1.5 MB of quota. Once you hit the cap, new mail is refused with 441.

How do I fix the AuthSMTP 441 quota error?

• Upgrade your data/message allowance in the AuthSMTP control panel, or wait for the monthly quota to reset.
• Reduce payload: compress or link to large attachments instead of embedding them.

What this error is not

Don't chase fixes for unrelated codes. A genuine 441 is not an authentication failure (those are 535/530), not a hard bounce for a bad address (that's 550/5.1.1), and not about TLS ports. There is no Gmail/Workspace "Less Secure Apps" angle here — if you landed on this page debugging Gmail auth, you want an App Password or OAuth2, not this code.