Package emailaddress provides a tiny library for finding, parsing and validation of email addresses. This library is tested for Go v1.9 and above. Parse and validate the email locally using RFC 5322 regex, note that when err == nil it doesn't necessarily mean the email address actually exists. Host validation will first attempt to resolve the domain and then verify if we can start a mail transaction with the host. This is relatively slow as it will contact the host several times. Note that when err == nil it doesn't necessarily mean the email address actually exists. This will look for emails in a byte array (ie text or an html response). As RFC 5322 is really broad this method will likely match images and urls that contain the '@' character (ie. !--logo@2x.png). For more reliable results, you can use the following method.