Invalid emails occurs when one sends an email to an address that doesn’t exist in the recipient email server or doesn’t meet the internet email format standards. This could also happen in case of a mistyped email address or if the ‘@’ sign or certain special characters are left out. This response can come from either the sender or the recipient server. This also occurs when one is making an email ID and it doesn’t meet the required format standards.
These are some of the causes for invalid emails -
Person changed email accounts - The person has switched to a different email address and has the old one still active. In this case, your email may be received but it will never be read. This is also possible if they changed position in the job or changed jobs, then the email ID may be cancelled or redirected to another person and the emails will bounce or be sent to the wrong person.
Domain is dead or server is down - If the domain is dead or the server is dead, then the email may not be delivered to the recipient. If the email server is down or email provider is out of business then the email may remain undelivered.
The best ways to avoid invalid emails is to validate the email address and clean up email lists on a regular basis. This can be done by an online service which will check the email lists to make sure the email is valid. It verifies the email addresses by checking the syntax and format, typo errors, checking it against domains the email address is hosted on and any other errors that could affect delivery of the email.
Invalid emails affect the deliverability of emails, open/click rates, conversion rates, and sender reputation. Sending emails to invalid email addresses is a waste of time, money and technical resources on non-existing contacts.