Which is true about pop3 and imap for incoming email?
both keep email on an email server by default
imap keeps email on an email server by default
neither keep email on an email server by default
pop3 keeps email on an email server by default.

IMAP keeps email on an email server by default is true about POP3 and IMAP for incoming email.

Explanation:

Post Office Protocol version 3 (POP3) is a standard mail protocol that can be useful for receiving emails to a local email client from a remote server . It helps in downloading email messages on the local computer and reading them when you are not connected in online. An important thing that is to be considered is when you are using POP3 for connecting to an email account, all the email messages will be downloaded locally and hence they are deleted from the email server. When there is a need in accessing the  account from different locations, it does not best suit your need.

The Internet Message Access Protocol (IMAP) is a email protocol that is helpful in accessing email on a remote web server from a local client. When your are using IMAP, the messages will not remain on the local device, like a desktop. It will be kept on the server.When there is a need in accessing the  account from different locations, it will best suit your need.

answer; the above statement is (true);