What are Soft Bounces
When you send out an email marketing campaign, you will most likely have some hard bounces and soft bounces. A bounce is a failure, the message did not reach the recipient.
A soft bounce is a partial or temporary failure, a hard bounce is a permanent failure. In this video we are going to look at the different types of soft bounce.
When an email fails due to a soft bounce, the recipient’s server returns an error code. These codes will help to give a clearer picture of exactly why it failed to reach the recipient.
#421 - Suspected mail bomb
A mail bomb means that the recipient’s server has detected that you are sending to lots of mailboxes at the same domain name, for example. Sales@abc.com, bob@abc.com, accounts@abc.com
Your recipient’s server will probably employ a rate limit, this means that they will only allow a set number of emails through to their domain name – in our example this domain being abc.com. So if you have 20 mailboxes that you want to reach at the same domain name, it’s likely that only the first few will be allowed though, the rest will be returned as a soft bounce.
#450 Mailbox temporarily unavailable
The recipient’s email server reported that it was temporarily unavailable. In most cases this is caused by a network error with the recipient’s server.
This could be for a number of reasons and in most cases the issue may be resolved by the time of your next send. So a soft bounce message is returned.
451 Error with subscriber’s mailbox
When receiving your email, the subscriber’s mailbox reported an undisclosed internal error during transmission of your message.
This is normally classed as a temporary issue. In most cases you can expect any outstanding issues to be resolved by the time of your next send.
#550 Recipient rejected message
This means that your recipient’s mail server had analysed your message and rejected it. This could be because it considered the content spam related, or a negative history attached to the sending domain, or the sending domain had not been verified.
#552 User’s mailbox is full
Most users have a storage limit on the amount of emails that they can store. The recipient email server reported that your subscriber’s mailbox was full. When a user’s mailbox is full, the recipient server will reject all incoming email until the user has made additional storage space available.
#517 Error with your send from address
Your recipient’s mail server will look at your address as part of the filtering process. If it fails the checks, it will returned as a soft bounce.
These tests will look to see if the sending address is valid, it could fail because a typo in your send from address for example.
#541 Subscriber’s server too busy
This can occur if the recipient email server is very busy or experiencing technical difficulties. The server either did not respond – or it took too long to respond.
#523 Message / send from settings issue
There was a problem with the content of your email or send from settings, this caused delivery to fail.
Now this could be for a number of reasons, these include:
- Content contains spam phrases
- Sending domain not verified
- Subject header line contains spam phrases
- Sending domain address is a generic – such as info@ or sales@
#400 Temporarily deferred
In this scenario the recipient server will initially reject your message, asking your service provider to try again at a later date.
Some service providers such as Yahoo will defer your message if there is a negative history attached, or if previous recipient’s have reported your mailers as spam
#575 Send from domain not authenticated
Nowadays, lots of service providers will only accept your email if it has the inclusion of an SPF record and a DKIM signature. This can be easily added to your domain and acts as a seal of authenticity that you are who you say you are.
#57606 Office 365 rejected
This code relates specifically to Microsoft’s Office 365, it is their own code that they use as a soft bounce definition. They have rejected your send because of negative history and/or other users in their network reporting your previous sends as spam
#418 Send from address does not exist
Recipient email servers will often validate your send from address. This code means that they have done so and could not find a record of the send from address that you’ve used as being a live address.
#569 Routing issue with subscriber
This may have been caused by a network or routing issue at your subscriber’s email server. It could be a temporary issue, so it’s worth try again later.
#0 Miscellaneous error with recipient server
This one is used by some servers as a bit of a catch-all. It’s a generic message that means additional info could not be provided, it therefore falls into the category or undisclosed – or miscellaneous.
Summary
OK, so there were are there’s a quick run down of the most common soft bounce reasons and the associated codes that may be returned.