Error: Lookups on activites must have a unique domain

Question

I'm using Salesforce lightning, and creating a lookup field in Activity object and referencing the lookup field to a custom object (Property).
I accidentally deleted the lookup field, and recreate again. Salesforce shows the following error

There were custom validation error(s) encountered while saving the affected record(s). The first validation error encountered was "Lookups on activites must have a unique domain. You can not have multiple relationships to the same object.".

I'm suspecting this is due to some internal referencing, but I have no idea how to resolve it.

Answer 1

When I deleted a lookup field in Salesforce Lightning, the deleted field will move to recycle bin and keep up to 15 days before Salesforce automatically remove it. To remove from the recycle bin, I have to switch from Lightning to Classic portal and delete it because Lightning does not have this function yet.

Answer 2

Make sure you really deleted the lookup field on the custom object page and not from the layout.

Answer 3

When the deleting s field in Salesforce, it is first deleted, with giving you a change to undo the delete.

If you have then deleted the field from the list of deleted fields, it might still not be deleted right away, in Salesforce, since it is a multi tenant environment, some jobs are scheduled to be run a bit later.

If the issue persists you might need to contact Salesforce to see if they can purge the field for you.

Answer 4

Thanks WenHau, that worked for me.

• user icon > Switch to Classic
• Setup
• Customize > Activities > Activity Custom Fields
• choose the field and Erase
• username > switch to Lightning Experience