List of result codes

Below are the meanings of most of the codes that can be returned by Shakelist after an analysis. Do you have questions about any of them? Contact us!

During each test, Shakelist returns two codes: a maincode and a detailedcode.
The first one allows you to have a quick idea of the functioning (or not) of the e-mail address.
The second gives more indication of the reason for the decision.

Main codes


The various tests performed by Shakelist seem to indicate that the address is valid and functional.


The tests indicate that the address does not work (or no longer works) and that it is not able to receive messages. This code is also returned when the address is classified as “dangerous” (see the associated detailed code for more information).


The tests carried out do not make it possible to know if the address works or not without carrying out a real sending. The detailed code gives more indication of the reason for this uncertainty.

Detailed codes


The address format is invalid and does not respect the e-mail RFC.


The e-mail address is not associated with a mail server. It can therefore not receive messages.


The mail server is not responding.


The e-mail address is clearly identified as invalid by its mail server.


This is the most common code returned with the status “NOTSURE”. This means that whatever address is tested, the mail server always indicates that it is valid. The only way to test these addresses is to send them a real e-mail.


The e-mail address is identified by Shakelist as a dangerous address not to be contacted.


The address is a “disposable” address. It is not reliable because it is not associated with a single recipient. This type of address is generally used by people who do not want to communicate their personal address. Never send confidential messages to such addresses.


The mail server associated with the e-mail address is classified as dangerous. Do not contact him.


The e-mail address is protected by a “greylist” system. The principle of a greylist is to temporarily refuse messages by indicating a temporary error. Once a certain time has passed, the email is accepted. Shakelist is one of the few solutions (the only one?) to test this kind of system. Nevertheless, for performance reasons, we limit the wait to a few minutes. If the time limit is exceeded, the address will be indicated as “NOTSURE” with this code “ERR_GREYLIST”.

Any questions?

Whether you are already a customer or not, contact us!
Our team will be happy to answer all your questions.