Can we do a mass update on survey responses?

I think you could send a Thank You message that includes a retake link. The format of a retake link is:
https://{yourbrand}.qualtrics.com/SE/?SID=${e://Field/SurveyID}&Q_R=${e://Field/ResponseID}&Q_R_DEL=1

Hi Tom,
We're not currently using the core xm product, just the surveying tool so we won't be able to send thank you messages as it's an anonymous url. That does complicate things, doesn't it?

If you have access to the workflow, then you can use the email task in order to send out the retake link as TomG mentioned. You can make use of the update response event in order to send out thank you surveys in bulk

https://community.qualtrics.com/XMcommunity/discussion/comment/43929#Comment_43929Too bad. The retake link would still apply, but how you build and distribute it becomes a lot more difficult.

Your SurveyID is the "SV_xxxxxxxxxxxxxxx" value associated with the survey project and the RespondID for each respondent can be obtained from downloading the Raw Data. Using Excel and concatenate, you should be able to construct the Retake links.
Then, you can use a Mail Merge in Outlook to distribute the Retake links to the recipients. Steps on how to do that are below
https://support.microsoft.com/en-us/office/use-mail-merge-to-send-bulk-email-messages-0f123521-20ce-4aa8-8b62-ac211dedefa4
https://support.microsoft.com/en-us/office/insert-mail-merge-fields-9a1ab5e3-2d7a-420d-8d7e-7cc26f26acff