Zoho CRM field gives anyone access to other records!?

Zoho CRM field gives anyone access to other records!?

Hi

Within CRM Id like to send a mass email to my contacts which contains a link to my Form which is prepopulated with their specific details. 

If I Insert Form within my CRM email this works fine. BUT I can only do this for one email at a time.

If I include a generic link to my form which I can include in mass emails, then it means they contact can enter someone elses email address which displays someones elses details! (obviously a massive security issue).

Ive tried dynamically building the link within my template like:

https://forms.zohopublic.eu/cubebusinesssolutions/form/Contactsupdateform/formperma/DrwzWxzkR-ESXzDXrpaxIT605PIJJx86Y?crm_entity_id=${Suppliers.Main Contact Id}

But this does not work.

So my question is: How can I send a mass email to all my contacts from my CRM where they click a link and it prepopulates ONLY their specific details?

Ive followed instructions such as https://www.zoho.com/forms/help/integrations/zoho-crm/update-record.html#upsert-limitations and no joy.

Thanks!