Sarah's email client allows her to download emails for offline access. However, when she deletes an email on her laptop, she notices it's still available on her mobile phone. Which email protocol is her client likely using?

Sarah's email client is likely using POP3 (Post Office Protocol version 3). POP3 is a protocol that downloads emails to the local device and typically does not synchronize actions across multiple devices. Emails are often downloaded and removed from the server, leading to discrepancies between devices.