This article explains the most common error messages you may encounter in your transaction log, what they mean, and how you can resolve them.
As a user of Addo Sign, you may occasionally experience that recipients or signers of a transaction are unable to complete the signing process or do not receive the signed document.
Below, we explain how to locate these error messages in the transaction log and offer guidance on how to troubleshoot them. In some cases, additional support may be needed. Please don’t hesitate to contact us at [email protected].
How to find error messages
When an error occurs during an active transaction, the status will typically be shown as Failed, and an error message will be available in the transaction log.
To view the error message:
Open the Overview page
Locate the failed transaction and click on it
Click on Signing details
Select the Log tab to view the error message
Note: A transaction may still show a status like Completed or Started even if an error occurred. This is because some errors do not stop the transaction entirely. We therefore recommend checking the log regularly to review the full status and identify any potential issues.
Types of error messages
Most errors typically occur either during the initial step, when the recipient is notified and receives a link to the signing page, or the final step, when the signed document is being distributed to recipients.
Below, we outline some of the most common error messages, explain what they mean, and provide guidance on how to troubleshoot them.
An error occurred while distributing the document
The document may be in an unsupported format, such as pages of different sizes or dimensions. It can also occur when distributing via Digital Post and the file contains embedded URLs or form fields.
Full error message:
An error occurred while distributing the document
To prevent this issue, make sure the document is:
Saved as a flat PDF (not interactive or containing form elements)
Free of any embedded URLs or data fields
This ensures the file is compatible with all delivery methods, including Digital Post.
For more information about Digital Post and their requirements, please refer to digitaliser.dk - Øget validering af filnavne og URI i Actions fra d. 10/9 2025.
Possible problem with delivering notification
This type of error usually occurs when the system is unable to deliver a copy of the signed document via the email distribution method, often due to an issue with the recipient’s email address.
To resolve the issue, you can reactivate the transaction and review the recipient’s email address for any typos. You may correct the existing address or replace it with a different one before resending the notification.
For step-by-step guidance, please see our article:
Recipient not found by SMTP address lookup
What does this mean?
This error indicates that the email address you entered does not exist or cannot be found by the recipient's mail server. The SMTP (Simple Mail Transfer Protocol) server attempted to look up the address, but it failed, resulting in a "RecipientNotFound" error.
Why does it happen?
A spelling mistake in the email address
The email address no longer being active
The domain being incorrect or outdated (e.g., @gmial.com instead of @gmail.com)
Full error message:
Possible problem with delivering notification. Please verify recipient details are correct and resend the notification. Error message: 550 5.1.10 RESOLVER.ADR.RecipientNotFound; Recipient not found by SMTP address lookup
Unknown recipient
What does this mean?
This error occurs when the recipient’s email address is not recognized by their mail server. The server is unable to deliver the message because the address is invalid, does not exist, or has been deleted or deactivated.
Why does it happen?
Typo in the email address
Email account no longer exists
Domain is incorrect or inactive
Full error message:
Possible problem with delivering notification. Please verify recipient details are correct and resend the notification. Error message: 550 5.1.1 Unknown recipient
Mailbox unavailable
What does this mean?
This error indicates that the email could not be delivered because the recipient's mailbox is not available. This can happen for several reasons, including:
The recipient's mailbox is full
The mailbox has been suspended, disabled, or deleted
The recipient’s mail server is temporarily unavailable
The address is valid, but misconfigured or blocked
Full error messages:
Possible problem with delivering notification. Please verify recipient details are correct and resend the notification. Error message: 550 5.5.0 Requested action not taken: mailbox unavailable.
Possible problem with delivering notification. Please verify recipient details are correct and resend the notification. Error message: 550 Requested action not taken: mailbox unavailable For explanation visit https://postmaster.mail.com/en/case?c=r1601&i=ip&v=159.183.2.37&r=1MYe2H-1u6RQk3323-00KtJH
The email account that you tried to reach does not exist
What does this mean?
This error means the email address you're trying to send to does not exist. The mail server attempted delivery but could not find a valid mailbox for the address.
Why does it happen?
A typo in the email address (e.g. misspelled domain or username)
The recipient's email account has been deleted or never existed
Extra spaces or formatting issues in the email field
Full error message:
Possible problem with delivering notification. Please verify recipient details are correct and resend the notification. Error message: 550 5.1.1 The email account that you tried to reach does not exist. Please try double-checking the recipient's email address for typos or unnecessary spaces. For more information, go to https://support.google.com/mail/?p=NoSuchUser af79cd13be357-7df157ec627si1195945785a.546 - gsmtp
Error dialing remote address: dial tcp ***.***.*.**:*->***.***.***.**:**: i/o timeout
What does it mean?
This error means that the system tried to send an email, but couldn’t connect to the recipient’s email server in time. It waited for a response but didn’t get one, so the process was canceled. Think of it like calling someone, but the phone keeps ringing and no one answers.
Why does it happen?
The recipient's email server may be down or not responding
There might be internet or network problems
Some systems block email traffic, especially on certain ports (like port 25)
What can you do?
Double-check the email address to make sure it's correct
Try again later. The issue may be temporary
If the problem continues, you can try a different email address or ask the recipient to check their email settings
Full error message:
Possible problem with delivering notification. Please verify recipient details are correct and resend the notification. Error message: error dialing remote address: dial tcp ***.***.*.**:*->***.***.***.**:**: i/o timeout
Bounced Address
What does it mean?
This error means that the email could not be delivered to the recipient and was returned (bounced) by their email server. In some cases, this may happen because the recipient is blocking emails from us.
Why does it happen?
The email was blocked by the recipient’s mail system
The recipient’s organization may have strict email rules and has blocked our sending domain: [email protected]
What can you do?
Ask the recipient to whitelist the sender address: [email protected]
Contact Addo Sign support at [email protected] and request to have the email address removed from the bounced list (Please note, this will require the receiver to first allow for emails from [email protected], otherwise the recipients email will return on the bounced lists.)
Full error message:
Possible problem with delivering notification. Please verify recipient details are correct and resend the notification. Error message: Bounced Address
The recipient's inbox is out of storage space
What does it mean?
This error means that the recipient cannot receive any new emails because their mailbox has run out of space. Until they free up space, emails sent to them will be rejected.
Why does it happen?
The recipient’s email account has exceeded its storage limit
Their email provider is temporarily blocking new messages until space is made available
What can you do?
Ask the recipient to clear space in their inbox by deleting or archiving emails
Request an alternative emailaddress from the recipient
Full error message:
Possible problem with delivering notification. Please verify recipient details are correct and resend the notification. Error message: 452 4.2.2 The recipient's inbox is out of storage space. Please direct the recipient to https://support.google.com/mail/?p=OverQuotaTemp d2e1a72fcca58-74eb9faf9e1si15687578b3a.321 - gsmtp
Recipient address rejected: Access denied
What does it mean?
This error means that the email was blocked or rejected by the recipient's mail server. The recipient’s organization has refused to accept the message, possibly due to their security or filtering settings.
Why does it happen?
The recipient’s mail server does not allow messages from the sender or domain
Strict filtering rules or policies on the recipient's side
The recipient's domain is configured to reject certain external messages
What can you do?
Ask the recipient to whitelist our sending address: [email protected]
Full error message:
Possible problem with delivering notification. Please verify recipient details are correct and resend the notification. Error message: 550 5.4.1 Recipient address rejected: Access denied. For more information see https://aka.ms/EXOSmtpErrors [AMS0EPF000001AD.eurprd05.prod.outlook.com 2025-07-11T10:11:10.746Z 08DDBF3A11D7CB8A]
Contact with cpr ********** does not exist
What does it mean?
This error means that Digital Post could not find a valid recipient linked to the provided CPR number. As a result, the document could not be delivered.
Why does it happen?
The person has opted out of Digital Post
The CPR number belongs to someone who is legally exempt (e.g. minors or certain protected individuals)
The CPR number is invalid or mistyped
What can you do?
Confirm the CPR number with the recipient to make sure it is correct
Check if the recipient is registered with Digital Post and able to receive digital mail
If delivery via Digital Post is not possible, consider using an alternative delivery method, such as email or secure file transfer
You can also download the signed document manually and send it directly
Full error message:
Possible problem with delivering notification. Please verify recipient details are correct and resend the notification. Error message: Contact with cpr ********** does not exist
Please note that we offer CPR validation. You can read more about it here:
Spam Reporting Address
What does it mean?
This error means that the recipient's email system has flagged the sender address as potential spam. As a result, the message was rejected or blocked.
Why does it happen?
The recipient or their email provider has marked previous messages as spam
The domain [email protected] may have been blacklisted or flagged in the recipient’s mail filters
The recipient's spam filter settings are too strict
What can you do?
Ask the recipient to whitelist the address: [email protected]
Have the recipient check their spam or junk folder
Contact Addo Sign support at [email protected] to check if the address is listed as bounced or blocked
Reactivate the transaction and resend it once the issue is resolved
Full error message:
Possible problem with delivering notification. Please verify recipient details are correct and resend the notification. Error message: Spam Reporting Address
Too Many Failed Login Attempts
What does it mean?
This error means that the signer entered incorrect information multiple times in a row, when for example trying to identify their identity by SMS code. To protect the transaction, the system automatically blocked further attempts and marked the transaction as failed.
Why does it happen?
The signer entered the wrong verification code, password, or login method repeatedly
The system triggered a security lockout to prevent unauthorized access
What can you do?
Reactivate the transaction so the signer can try again
Contact the signer and confirm they are using the correct login method (e.g. MitID, SMS code, or password)
Make sure the signer understands the required steps before retrying
Full error message:
Transaction failed because signer attempted to login unsuccessfully too many times