Dropbox Sign Logs and emails can include entries referencing API callback errors, some of which can be avoided by following best practices for handling outstanding signature requests which no longer require signing.
Please be sure to cancel — and not delete — signature requests which should no longer be pending. Deleting orphans the signature requests and will result in 7 failed callback retry emails.
Avoiding these emails is easy. Please terminate signature requests by opening the request and clicking “Cancel Request".
Do not delete signature requests.
TIP: For admins interested in seeing which users may be unaware of this best practice, deleted signature requests can often be found in the SFDC Recycle Bin.