Zenu performs a number of checks on each email address to verify that the email is technically valid and legitimate. The following factors are checked:
Verify email address format; ensures the email address is in the correct format e.g., [email protected]
Check MX Records; we check the domain server to ensure that they have a Mailbox set up
Check for SMTP; SMTP is the standard protocol used between servers and users to allow for the sending and receiving of emails
Check against a spam score; we use a third-party application to cross-check email addresses that are flagged with a negative spam score. Emails with a bad score are treated as invalid emails. Quality scores are based on appearance, deliverability and whether the email is a disposable email or not.
These checks help to ensure that email addresses entered into the system are technically valid emails.
Although you may experience some emails operating functionally, they may not be correctly set up which can cause issues in email routing, hence they would be flagged as invalid due to technical failures.
If an email is invalid, it may have been marked invalid due to a temporary error as per the above checks or perhaps there could have been a hard bounce which would also cause it to be marked as invalid.
The sender of an email should receive an error report from the hard bounces and the error report will state why the email failed to be received (in most circumstances it is because the email address may not exist).
There are a number of websites you can use to independently cross-check the validity and operation of email addresses:
Each one will provide different results based on what they check. Some may appear as valid, others may return the same email as invalid.
If you believe that an email address is in fact valid, you can re-validate it from the contact's page by clicking on Validate Email on the Details tab of the Contact page:
Please ensure that you are thorough when revalidating emails, as sending emails to addresses that are constantly invalidated can cause the domain to be suspended or repeated abuse can lead to a global blacklisting across major email provider networks.
If an email is sent to a contact's email address and it bounces, this will also mark the email address as invalid to prevent any more hard bounces.