Skype has a Click to Call browser plugin that allows you to click numbers in web pages and emails to start a Skype call. Unfortunately, this plugin will insert its own HTML code into your Email where it finds telephone numbers, causing problems for your recipients when you come to send it.
In order to avoid the issue, we recommend that that you follow these steps to disable Click to Call.
To fix an Email that Skype has changed, you may need to delete the Block in question and re-add it from your Block Library.