Airtable: Attachment url issue when sending emails

When sending generated files as an attachment, you might run into the following issue:

The most likely reason for this issue is that by the time the automation fires, the attachment isn't fully uploaded to Airtable's data storage. The workaround is to wait for the presence of the file by using a formula field and matching the URL path of Airtable's file storage. It is described here on Airtable's support page: https://support.airtable.com/docs/troubleshooting-airtable-automations (search for "An attachment URL is disallowed").