Has anyone ever used an email validation API?

I worked at one company that used them (after a domain was disabled for high bounce rate). We found that most of the invalid emails were from transcription errors, typically typos in yahoo.com, gmail.com etc. Most don't catch the none@email.com type of errors, although frankly those are easy enough to validate yourself. My general feeling is that if you're collecting emails electronically you don't need it, but if the email list is created via someone doing data entry for paper records, then they're helpful.

Sure, this could be a critical customer requirement.

Use case: A client has signed up for a service and is paying to receive a report. In this case, they receive a link to download. No tracking embedded in emails.

Verification: 2 review cases. Monthly review.

Case 1: Email bounces from server.

Case 2: Email doesn't bounce but not checking report.

In both cases, sales/customer service get in contact with the customer.

For Case 1, to check an appropriate email address (client contact leaving, mailbox full/disused, etc).

For Case 2, largely to check if reporting can be more useful (i.e. actually look at the report) which can result in interesting ideas about better integrating into their workflow/needs, though spam-whitelisting is also sometimes a factor here.

I tried the links you provided with an email address on my personal domain that I know not to be deliverable, and it was reported as deliverable.

Do you have any issue with the ESP for high bounced rate? If yes, then cleansing is a good way to recover from it.

Otherwise, your list is just fine and you do not need to have email validation.

validation Api, nice argument i would read more about that