The email addresses have expired.
Create auto expiring inboxes using MailSlurp disposable mailboxes. Email accounts that expire and self destruct.
MailSlurp inboxes can be set to expire at a given time. The server periodically checks inboxes to see if they have expired and archives those that have.
Expired inboxes
You can view inboxes that have expired with the ExpiredInboxRecord endpoints in the inbox controller or in the dashboard.
Emails
Expired inboxes can no longer sender or receive emails. You can however view old emails using the inbox's ID.
Expiration causes
If you have a free account a default expiration date is used when creating inboxes. Paid accounts can set whatever expiration dates your desire or leave the property blank for permanent inboxes by default.
Permanent inboxes
To ensure permanent inboxes use a paid account or upgrade your account.
Working with expired inboxes
See the developer documentation to list and fetch expired inbox details.