There is an ongoing outage on the primary CPAN mirror. It is possible to work around the issue by using MetaCPAN as a mirror.
To install PHP::Functions::Mail, copy and paste the appropriate command in to your terminal.
cpanm
cpanm PHP::Functions::Mail
CPAN shell
perl -MCPAN -e shell install PHP::Functions::Mail
For more information on module installation, please visit the detailed CPAN module installation guide.