You can construct the AEM url in the sling model and use the same while sending email.
1. First get the current page path using Page object.
@inject
private Page currentPage;
2. Use Externalizer to get the hostname and the construct complete url ("<hostname>" + "/editor.html/+"<Page path>"+"html"
you can check below example to get hostname info.
https://experienceleague.adobe.com/docs/experience-manager-64/developing/platform/externalizer.html?...