Hard and soft bounces

What a hard bounce and a soft bounce mean in your logs, how Mailyoto retries, and what to do about each.

Updated 29 October 2026

A bounce is a destination’s server refusing an email that Mailyoto tried to deliver.

A soft bounce is temporary: the server may accept the email later. A hard bounce is permanent: the server won’t accept it.

In your logs, a soft bounce is a Deferred event, and a hard bounce is a Failed event.

How Mailyoto handles each#

Mailyoto reads the response the destination’s server sends back, and decides from its code and text whether the refusal is temporary or permanent.

In the entry’s events	Status in the list	What Mailyoto does
Deferred	Retrying	Tries again later.
Failed	Failed	Stops trying, and emails the sender a notice.
Returned	Failed	The server accepted the email, then sent a bounce report later. Mailyoto passes the report on to the sender.
Rejected	Failed	Not a bounce. Mailyoto turned the email away when it arrived, and the sender’s server got the refusal.

After a soft bounce, Mailyoto tries again 2, 5, 30, 120 and 720 minutes after each failure. That makes 6 attempts over about 14.6 hours.

If the last attempt fails too, the entry ends with a Failed event.

Some destinations refuse the first attempt from any new sender and accept a later one. The retries cover that.

When an email to an alias with 1 destination fails permanently, Mailyoto emails the original sender:

From: no-reply@bounces.mailyoto.net
Subject: “Message not delivered”
It begins: “Your message could not be delivered. The receiving server rejected it permanently, so no further attempts will be made.”

Cause	Usually	What to do
The destination mailbox is full	Soft, sometimes hard	Free up space. Mailyoto blocks the address for 72 hours, or until a delivery test passes. See blocked destinations.
The destination’s server is busy or down	Soft	Nothing. The retries usually deliver it.
The destination address doesn’t exist	Hard	Correct the destination on the alias. Mailyoto usually blocks the address.
The destination refuses the email as spam	Hard	See forwarded mail that lands in spam.
The email is too large for the destination	Hard	Ask the sender to share large files as a link.

The Response line in the entry’s details quotes the server’s reason. Read it before you change anything.