Web Giving, Interrupted
When sending eblasts, it is important to put the phone number in body copy using a format that let's the user dial the number by clicking on it.
Because more people are reading emails on their smartphones, but not pledging through those devices. The opportunity to get people to act is as they are reading the email. You just can't count on them remembering to reopen the email at a later time.
Until giving via a mobile device is as easy and common as over a computer, you'll want to extend the recipient's giving options by making it easy to call in a contribution when the email is first opened.