1and1 is a web hosting company by Ionos. You can use your 1and1 email account with any other email program and do your 1and1 Imap settings.
Let us just add that whatever email account you want to connect the 1and1 account to, you can easily choose the automatic configuration. The first step is to choose if you are opting for a POP3 or an IMAP configuration.
The common information required for any email settings is the Username and Password.