Email Delayed or Stuck: "Message Has Not Yet Been Delivered" Print

What the message means

If you receive an automated notice similar to:

Warning: message still undelivered after 4 hours. Will keep trying until message is 3 days old.

your email has not bounced and has not been lost. The receiving server could not accept it right now, so our server has queued it and will keep retrying automatically. No action is needed from you yet, in most cases the message delivers on a later attempt without you doing anything.

This is a temporary condition, which is different from a bounce. A bounce is permanent and tells you the message will never be delivered. A delay notice tells you delivery is still being attempted.

Why mail gets deferred

• The receiving server is busy, down, or under maintenance. Common with smaller company mail servers, and usually resolves within hours.
• The recipient's mailbox is full. Some servers defer rather than bounce when a mailbox is over its limit, hoping space frees up.
• Greylisting. Some receiving servers deliberately reject the first delivery attempt from a sender they haven't seen before, and accept the retry. This is a common anti-spam technique and typically only delays mail by minutes.
• The receiving server is being cautious about reputation. If it is temporarily rate-limiting or double-checking the sending server, it asks for a retry rather than accepting immediately.
• A DNS problem on the recipient's side. If their domain's mail records are misconfigured or mid-change, delivery attempts may fail temporarily until the records settle.

What to do

1. Within the first few hours: nothing. Do not resend, a resend just adds a second copy to the queue and the recipient may eventually receive both.
2. If it is urgent, contact the recipient another way and confirm their mailbox is working and not full.
3. If you keep getting delay warnings for the same recipient over more than a day, the problem is almost certainly on their side. Let them know through another channel so they can raise it with their own provider.
4. If mail to many different recipients is all being delayed at once, that pattern points at something wider, open a support ticket with us and include one of the delay notices so we can check the mail queue and the server's sending reputation.

How long will it keep trying?

The delivery attempts continue automatically, with the interval between retries growing over time. If the message still cannot be delivered by the deadline stated in the notice (typically a few days), it is returned to you as a permanent failure, and at that point you will need to resolve the cause before resending.

Good to know

Delay notices are sent by the server, not by a person, and receiving one does not mean anyone has read or rejected your message. If you send newsletters or bulk mail, a sudden spike in deferred messages across many recipients is an early warning sign worth acting on, see our article on the "Max Defers and Failures Per Hour" limit, since sustained deferrals count toward that hourly threshold.