Emails are being tracked by a tracking pixel. This is simply a 1 pixel GIF image in the source code of email messages sent by Mautic.
When an email is opened by an email client like Outlook, Thunderbird or GMail, the client tries to load the images in it. The image load request is what Mautic uses to track the email open action.
Some email clients have auto loading images disabled, and users have to click on a "Load Images" button to load images inside an email message.
If the images aren't loaded for this reason or another, Mautic doesn't know about the open action. Therefore, email open tracking is not 100% accurate.
Before an email is sent, Mautic replaces all links in the email with links back to Mautic including a unique key. If the contact clicks on such a link, the contact is redirected to Mautic.
Mautic tracks the click action and redirects the contact to the original location. It's fast so the contact doesn't usually notice the additional redirect.
If the email click doesn't get tracked, make sure that:
hrefattribute is absolute and valid. It should start with http:// or https://.
The unsubscribe link doesn't work in test emails.
This is because the test emails are sent to a Mautic user and not to a Mautic contact.
Mautic users cannot be unsubscribed and therefore the unsubscribe link looks like this:
https://mautic.example.com/|URL|. However, the link will work correctly when you send the email to a contact.
Best practice is to create a segment with a small number of users to receive test emails (for example, yourself) - this will ensure that you can fully test features such as unsubscribe behaviour.