IMAP and POP3 are standard email protocols that you can use to access email messages from Lookafter servers via your mail client (Microsoft Outlook, Mozilla Thunderbird, Apple Mail, mobile mail client, etc).
POP (Post Office Protocol) is a very simple protocol that only allows you to download emails from the server (your webmail) to your device in a one-time manner. You can configure to leave a copy of messages on the server to be downloaded again later (by other devices), but there is no two-way synchronization between the mail server and your mail client.
IMAP (Internet Message Access Protocol), however, provides a better method to access your emails from multiple devices. If you check your emails on webmail, on MS Outlook, and again on your mobile phone, IMAP ensures that emails are always accessible from any device at any given time.
If you are deciding which protocol to use, we suggest you to use IMAP.
As POP3 is prone to losing email messages or downloading the same messages multiple times, IMAP offers a more stable experience with its two-way synchronization capabilities between your webmail and mail client. Any email messages you read, move or delete will be updated across all devices. No matter which client you use, you will see the same Inbox. If you are more concerned about storage quotas and privacy issues, then for this case, POP3 would be better than IMAP.