Terry,

Recalling messages is not a function of SMTP server, but email clients. For example, when using Outlook, you could submit a request to recall a message. See the image below.

However, once an email message is sent and delivered to the destination server, there is no mechanism to take it out from the recipient's inbox. Therefore, most recall mechanisms end up sending another email with the word "Recall" in the subject line asking the recipient to ignore the earlier message.