If any user has bookmarked your old domain, they will not be able to access your new website unless you set up a proper redirect from the old domain to the new one. Failing to do this can lead to significant issues, as visitors trying to reach your site through the old URL will encounter errors or dead links. This not only frustrates users but also negatively impacts your website's SEO rankings. Search engines may treat the old URLs as broken, which can reduce your site's authority and visibility in search results. Additionally, backlinks pointing to the old domain will lose their value if not redirected, causing a loss in referral traffic and weakening your overall online presence. Therefore, implementing domain redirects is essential for maintaining SEO health and user experience.