Hello,
if I use an anonymised survey I have a field refurl in my answer table.
Often this shows a reference link from the webmail client used by the participant.
This could give a hint on the email provider uses and therefor might impact the anonymity of the participants.
This looks like a privacy issue to me.

Any ideas on this or how to fix this in my setting?

Cheers, Jan

Well, it's up to you.
When activating a survey you are asked.
 
So set it to "No".

"Yes"
 

"No"
 

Joffm