I reported this before and it was marked as fixed.

I still receive emails like this one:

Hi Administrator,  An error has been logged at X.  #3S127/4 We could not find your account in order to unsubscribe you from emails. Error triggered by: Guest (207.1.1.49) 07/08/2016 in System Further information on this error may be available by viewing the Error Log Viewer tool in your Admin Control Panel.

 

This happens in the following scenario:

1. User received a message

2. User unsubscribes (probably correctly)

3. User continues to click the Unsubscribe link multiple times

Submit a ticket in your Client Area for direct IPS assistance. 

I still get these daily since converting.

12 minutes ago, ajmboy said:

I still get these daily since converting.

Have you since submitted a ticket?

Yes. There is a new error message in 4.1.6. From support below:

Quote

This error is occurring because the unsubscribe link has expired. This will occur if the user has altered their email address or password after the email was sent. I have edited the error message displayed so that if this occurs the user will be prompted to log in to adjust their settings to revalidate their account. This change will be included in 4.1.16

 

I have the same problem with a user in IPS 4.1.18.2

Please, @AlexWebsites how to fix this with the user?

On 19/10/2016 at 11:09 PM, AlexWebsites said:

log in to adjust their settings to revalidate their account

 Can you explain me the procedure?

Many thanks.

9 hours ago, pequeno said:

I have the same problem with a user in IPS 4.1.18.2

Please, @AlexWebsites how to fix this with the user?

 Can you explain me the procedure?

Many thanks.

Did you convert your site? This has to do with the converter and users logging in for the first time after conversion. They can't unsubscribe from the email until they log in at least once to re-validate their account after conversion. I converted a site from vbulletin where this was happening.

Hello @AlexWebsites Yes, i convert but  several years ago, and other users don´t have this problem.

The only explanation is that that user has not logged in since the conversion.

Exactly. This is why the converter stays in place.