If you want your customers to be able to call you straight from your sent campaign, you should consider implementing a visible Call now button in the newsletter’s body. Creating a “Call now” button is pretty simple – first, you will need to insert a button element into the selected section.
When that’s done – button’s “link” section should have shortcut: tel:phone number
for example, tel:+443031237300
Now when the recipient clicks on the button, an option to call the selected phone number will emerge.
Here how it looks on iPhone: