Signature and Sender name are tags that are in Red.
These tags are not replaced during preview. They are replaced when the message is sent. This is because when the message is sent, the platform automatically assigns a mailbox or LinkedIn account from the Accounts tab of the campaign to send this message. It now replaces the tag with the name & signature of the mailbox.
IMPORTANT
Ensure you have the signature and sender name updated for each mailbox and LinkedIn account.
Go to Accounts page -> Click on a mailbox or LinkedIn account -> Find Name and Signature under Settings -> Update it and hit Save