When we indicate that the email address is not valid, it means that we tried to send a message but that the email was refused.
There are several reasons for this. In most of the cases,
(Email Address Errors) Sometimes it’s literally as simple as just a mistyped or misspelled email address.
(Lack of Storage) Occasionally Walter email simply hasn’t got enough space to land.
(Permission Denied) This means the recipient’s mail server mistakenly thinks you’re spam.
For resolving this issue, the resident must add firstname.lastname@example.org to their list of valid emails.
This can be done in most cases by adding email@example.com to their contact list. In other cases, in the parameters / Filters and blocked addresses,
you must create a list and add firstname.lastname@example.org.