How to check if an Address exists?
If we find that the address does not exist, you will find one of the following scenarios with the appropriate rating.

Checkpoint: In some cases, you will find that an existing address can be found in a different locality. Always mark such cases as Incorrect – Address does not exist AND NOT Incorrect – Locality.
Please review following sections of Search guidelines to find more information and examples on ADNE topic:
7.2. Address Does Not Exist
10.3. Query Address does not Exist
User Query: Rua de Trás dos Quintais, 84, Azambuja
Result: Rua de Trás dos Quintais, 84
Address: Rua de Trás dos Quintais, 84, 2050-322, Azambuja
For this result, we first research on the postal office website. Since the postal office did not return a street range, we assume that the street number exists and we go to the next step.
Now we try to locate the correct location. However, on street imagery, we could verify that the last door on the street has the number 78 (https://bit.ly/2UOaJ61).
For this reason, we can be sure that the street number does not exist. This is because, in Portugal, street numbers are sequential even numbers on one side of the street, and sequential odd numbers on the other side. So, if the last number of the even side is 78 and our result is 84, the street number does not exist. To conclude, the correct ratings will be:
Relevance: Excellent
Name Accuracy: n/a
Address Accuracy: Incorrect – Address Does Not
Exist Pin Accuracy: Can’t Verify
Relevance: [EXCELLENT] According to the Guidelines 10.3. Query Address does not Exist, query requests a non-existent number. The result returned is the same as the queried address and should be rated as Excellent.
Name: [N/A] The result is an address, therefore according to section 6.1. Name Not Applicable (n/a), address type result does not have a name/title, the rating should be n/a. This is an address result, so the correct rating is n/a.
Address: [INCORRECT] This address does not exist – [https://bit.ly/2DzYYHY], street just goes to street number 78. Therefore, according to section 7.2. Address does not exist; the rating should be Incorrect – Address does not exist.
Pin: [Can’t Verify] Since the address does not exist, we are unable to confirm the correct pin location, according to section 9.1.5. Can’t Verify (Smallest Identified Area), when the address does not exist, we should rate the pin as Can’t Verify.