You can use a rule like this 

As you can see the field are now grayed out. 

​@Daniel Söderlund, Thanks for this. I tested it on the FreshService portal. While it did remove the ability to search for a requester, the field itself wasn’t actually disabled. This means you can still delete the requester’s email, but you can’t search for or select another one to replace it.

Hi, you can try altering some settings under Admin → support portal. 

First, you can change the radio button option for “Allow logged-in users to search for requesters when creating tickets or service requests” to “No” as shown below:

Then, you can add domains from which users can be created by adding domain names under “Email domain restriction”, this would not allow users from different domain to login. Hope this helps in any way !

Strange it’s disabled for me on my trial when I set it exactly like that. 
You assumed a requester when you tested? 

Noticed a bug if you have a password manager that can fill in fields it will change the value even if you can’t. 

Current Behaviour in Freshservice (Requester Support Portal):

• When customers log incidents via the support portal, they can manually input any email address in the Requester field (if that field is visible and editable).

• If they enter an email address other than their own (e.g., on behalf of a colleague), and that email is not already a contact, Freshservice auto-creates a new contact.

• This can:

  • Create unauthorised or unaudited users.

  • Skew ticket assignment and tracking.

  • Introduce security or compliance concerns (unauthorised requester identities).

We have had a combnation of the etioned issues occur and as I have used business rules for forms to fix  number of form fields in the past I thought the ideal scenario would be to diable the field for use - therefore allowing it to be read only and not valid for editiing. If this did not work I would just hide it from the INC form.

 

I found I was unable to do any and cannot find a valid workaround that removes the ability for end users to amend/edit this field.

 

I’m looking for a solution to this if anyone has been able to resolve.

You can use a rule like this 

 

As you can see the field are now grayed out. 

 

 

I tested this in prior days but thank you for re-raising to my attention as with some portal specifc tweaking this has worked and has made the Requester field effectively read-only.Thanks all for input and the quick response.

For anyone interested, I also found the below addition under Admin > Rebrand your service desk (Within the footer) provided the same read-only condition.

<script>
jQuery(document).ready(function(){
    setInterval(function() {
        if (window.location.href.includes('/support/tickets/new')) {
            var requesterField = jQuery("#helpdesk_ticket_email");
            if (requesterField.length && !requesterField.prop('disabled')) {
                requesterField.prop("disabled", true);
            }
        }
    }, 200);
});
</script>