Web server: Apache, NGINX, lighttpd or other with PHP support

PHP: 5.4 and above

PHP extensions: cURL, iconv, json, libxml, dom, openssl, DateTime, PCRE, SPL

Browser: Google Chrome, Firefox, Opera 10+, Safari 3+, Internet Explorer 11 or EDGE

Optional: PDO (MySQL/PostgreSQL/SQLite) PHP extension (for contacts)

RainLoop webmail was designed with efficient memory use in mind, so it can work fine even on low-end web servers.

Regardless of mailbox size and number of mails in it, memory use per active user is always kept at a minimum, even when very large mails are processed.

In most cases, application speed directly depends on mailserver performance and network bandwidth available.

In addition, built-in caching system allows for improving overall performance and reducing load on web and mail servers.