Why is there a blank square in an email regarding an announcement including a hyperlink?

If you are experiencing a blank space in an announcement email, which includes a hyperlink in your message, the format must have to do with the copy-pasting content into the announcement.

If you use the </> button in the Announcement content, there is a lot of hidden code. The code is imported to the content when you copy paste it from somewhere else (E.g. from a Word Document or from a Web Page). 

To prevent this, you can use the lx button for future announcements. This button is intended to "remove all external formatting". Try removing the lx to remove all external formatting.

If we take the example below, you can see the sequence target="_blank" style="background-color: rgb(255, 255, 255); which is what tells the announcement to put a blank back-ground.

Example:

<p>The following is to inform you of changes in the Sales Support team. See <a href="https://login.hrwize.com/hr/documents/view/doc/5b2710d590044b46d90bb308ef1df10c.pdf" target="_blank" style="background-color: rgb(255, 255, 255);">HERE</a> for more details / Par la présente nous désirons vous informer de changements au sein de l'équipe de soutien aux ventes. Lisez <a href="https://login.hrwize.com/hr/documents/view/doc/5b2710d590044b46d90bb308ef1df10c.pdf" target="_blank" style="background-color: rgb(255, 255, 255);">ICI</a> pour plus de détails</p>