Solve an email problem (following an error report)

This guide helps you identify and correct most of the email errors encountered after sending an e-mail to a recipient Be aware of this other guide if you are looking for information about errors obtained when setting up an email address in a software/mail client.

Preamble

• In general, an error message at the email level follows on from...
  • ... a poor configuration of the domain name used with your mail,
  • ... a problem at (the email provider of) your recipient.
• In any case, a delivery failure report ( Mailer Daemon or Mail Delivery Subsystem) containing the explanation is sent to the sender.

Search and identify mail error

When your message does not reach your recipient, a first failure report (Temporary Delivery Failure Report) is sent and specifies that the server will try to return your message several times.

A final non-remission report (Final Delivery Failure Report or Undeliverable Mail) sent by the correspondent's server is sent to the sender (via a pass through the Infomaniak mail server, hence the mention of Infomaniak at the beginning of most error messages that you can receive) to inform him that the email could not be delivered even after several attempts.

The notification shall contain: Always the reason for failure. Example below:

This is the mail system at host smtp-1-1234.mail.infomaniak.ch.
I'm sorry to have to inform you that your message could not be delivered to one or more recipients. It's attached below.
For further assistance, please send mail to postmaster.
If you do so, please include this problem report. You can delete your own text from the attached returned message.
The mail system anna.a@abc.xyz: host mxbw-abc-xyz.abc-ab12.abc.ch[123.456.789.00] said: 550 5.1.1
anna.a@abc.xyz recipient rejected, account administratively disabled (in reply to RCPT TO command) 

So here your correspondent's address is visibly suspended by his courier provider (account administratively disabled).

Sometimes you have to look for the reason for the error message received from its attachments (often a plain text file). Example:

Reporting-MTA: dns; mxbw.abc.ch‍ [123.456.789.00]
Received-From-MTA: dns; smtp-1-1234.mail.infomaniak.ch [12.345.678.99]
Arrival-Date: Tue, 01 Aug 2023 15:49:22 +0200
Final-recipient: rfc822; anna.a@abc.xyz
Diagnostic-Code: smtp; 552 RCPT TO:anna.a@abc.xyz‍ Mailbox disk quota exceeded
Last-attempt-Date: Tue, 01 Aug 2023 15:49:22 +0200

Here the mailbox of your external correspondent to Infomaniak seems full (Mailbox disk quota exceeded).

Most common cases

FPS Impaired

The SPF (Sender Policy Framework) record is not properly configured:

Subject: Delivery Status Notification (Failure)
From: Mail Delivery System mailer-daemon@domain.xyz
To: Anna.A anna.a@abc.xyz
This is an automatically generated Delivery Status Notification.
Delivery to the following recipient failed due to SPF failure:
anna.a@abc.xyz
Technical details of SPF failure:
The sender's domain domain.xyz does not have a valid SPF record. Please contact your email administrator to correct the SPF configuration.

Solution: check the configuration of your domain name and in particular SPF type registration if your website is hosted by Wix or another provider.

User Unknown

The e-mail address specified in the message is invalid or does not exist:

Subject: Delivery Status Notification (Failure)
From: Mail Delivery System mailer-daemon@domain.xyz
To: Anna.A anna.a@abc.xyz
This is an automatically generated Delivery Status Notification.
Delivery to the following recipient failed permanently:
anna.a@abc.xyz
Technical details of permanent failure:
The email address does not exist. Please check the recipient's email address and try again.

Solution: carefully check the recipient's e-mail address and correct it if necessary; make sure you use a valid e-mail address for the recipient.

Temporary Failure

Le serveur de messagerie du destinataire rencontre des problèmes temporaires ou est indisponible.

Solution: wait a while, then try again to send the message later. If the problem persists, contact the recipient's technical support for assistance.

Blocked by SPAM Filter (or Content Rejected)

The recipient's email server blocked the message due to anti-spam filtering rules:

Subject: Delivery Status Notification (Failure)
From: Mail Delivery System mailer-daemon@domain.xyz
To: Anna.A anna.a@domain.xyz
This is an automatically generated Delivery Status Notification.
Delivery to the following recipient failed due to the message being rejected as spam:
anna.a@domain.xyz
Technical details of delivery failure:
The content of the message triggered the spam filters of the recipient's email server. Please review the message content and try again.

Solution: check if your message contains elements that may be considered spam (keywords, suspicious links, etc.). Contact the recipient to see if the message has been filtered into the unwanted mail folder.

Be aware of this other guide on spam Out and this other guide on spam Incoming.

Bad Reputation

The recipient's email server blocked the message due to anti-spam filtering rules:

gmail-smtp-in.l.google.com said: 550-5.7.1
Our system has detected that this message is likely suspicious due to the very low reputation of the sending domain.
To best protect our users from spam, the message has been blocked.
Please visit https://support.google.com/mail/answer/188131 for more information.

Solution: check the reputation determine if there has not recently been an involuntary exploitation of one of your email addresses for malicious purposes, e.g.

Domain Not Found (or DNS Error)

Le nom de domaine du destinataire n'a pas pu être résolu ou n'existe pas.

Solution: Check the spelling of the recipient's domain and correct it if necessary; make sure that the domain name and DNS are valid and active.

Mailbox Full

La boîte de réception du destinataire est pleine, empêchant la réception de nouveaux messages.

Solution: inform the recipient of the situation and ask them to free up space by deleting e-mails or archiving items.

This cannot happen with e-mail addresses managed by Infomaniak since they do not have no storage size limit.

Part of their network is on our block list

If the error message (obtained in principle as a result of sending from an online tool, placed on the server where your website is located, e.g. an order confirmation from the Prestashop or other online store you manage) contains the following:

host hotmail-com.olc.protection.outlook.com[104.47.30.97] said: 550 5.7.1
Unfortunately, messages from [89.123.456.789] weren't sent. Please contact your Internet service provider since part of their network is on our block list.

Solution: Change the method of sending emails. The shipment is Unauthenticated and leaves from the server with a specific IP address that is apparently blocked by the recipient for any reason (Infomaniak does not intervene to request a release). It is therefore necessary to configure the online tool to perform authenticated consignments.

Less frequent errors

Deferred - Delayed

Error message Deferred - Delayed - Warning: message still undelivered after 4 hours, Will keep trying until message is 3 days old means that the Infomaniak email server has tried to connect to your correspondent's email server to send the message but for some reason has not been able to do so. This error message specifies that the Infomaniak server will continue to try to send your message during the period specified in the error message. If, after this delay the message has still not been distributed, you will receive a final error message stating that your message could not finally be distributed and therefore your correspondent did not receive it.

Greylisting Delay

This error Greylisting Delay happens when your recipient's mail server uses, like Infomaniak, a technique called "greylisting"which imposes a temporary time limit on the first attempt to deliver a message from an unknown sender. The Daemon Mailer may eventually send an error report indicating that delivery has been delayed due to the greylisting. Error may also mention banned sender You must return your shipment a few minutes/hours later.

Message Size Exceeded / File Too Large

These errors Message Size Exceeded / File Too Largeoccur when the size of the message (or attachments) exceeds the limit allowed by the recipient's mail server. The Daemon Mailer will return an error report indicating that the delivery failed due to the exceedance of the message size.

Rate Limit Exceeded

This error Rate Limit Exceeded occurs when the sender has exceeded the frequency or volume limit allowed by the recipient's mail server. Mail servers can impose limits to prevent spam or system overload.

Malware message rejected

This error Malware message rejectedoccurs when the message contains an attachment, a link to a Dropbox-type storage site or dynamic content including in the "transmitted" part of the message (in the case of a "forward" message, e.g.). Try to return the message from the web app Mail Infomaniak (online service) mail.infomaniak.com) instead of an email application, and eliminate any content that could cause this error.

The message contains a unicode character in a disabled header

This error The message contains a unicode character in a disallowed header may appear if you have inserted a special character like a heartr♥e.g. in the body of the mail, the subject or especially in the full name The risk of being refused by suppliers is very high: it is necessary to remain as simple as possible in the use of signs, characters and fonts.