Composer install problem

[BenjaminHoegh]

Problem 1
    - Installation request for ddeboer/imap ^0.5.2 -> satisfiable by ddeboer/imap[0.5.2].
    - ddeboer/imap 0.5.2 requires ext-imap * -> the requested PHP extension imap is missing from your system.

  To enable extensions, verify that they are enabled in your .ini files:
    - /usr/local/etc/php/7.1/php.ini
  You can also run `php --ini` inside terminal to see which files are used by PHP in CLI mode.

[RikudouSage]

You need to install the php imap extension. On Ubuntu etc. it's as easy as apt install php-imap.

[ddeboer]

Yep, as documented in the readme. 😄