MailMerge365 redirects any links you have in your email to our servers for recording the link to show in your dashboard. By default all links use the same URL (for example: http://alink.re). In order to increase delivery and response rates it can help to use a custom tracking domain. So you would buy a short url or use a subsdomain of your company domain (for example: links.example.org) and set this in the MailMerge365 options. Then all your emails will use that domain (which still points back to our servers so we can track the link) in the emails instead of the default one.