MailTester is an email verification software that offers tools to verify the validity and deliverability of email addresses. It aims to help users clean and maintain their email lists by identifying invalid, inactive, or otherwise problematic addresses that could negatively impact mailing performance or sender reputation. The platform provides a straightforward interface for users to input individual email addresses or upload entire lists for verification. Key features typically include syntax checking, domain validation, mailbox verification, and result reporting. By ensuring the accuracy of email data, MailTester helps businesses improve deliverability rates and maintain efficient and effective email communication.