IMAPdump, requires OpenSSL to be installed. Install it using the following command:

$ sudo apt install openssl

The IO::Socket::SSL Perl module is also required. First, install using the following command:

$ sudo perl -MCPAN -e shell

Then enter the following command from within the cpan shell:

cpan[1]> install IO::Socket::SSL

Now IMAPdump should run without errors. You can download it from https://github.com/andrewnimmo/rick-sanders-imap-tools.