Rainloop

# Install rainloop
 1) # wget https://www.rainloop.net/repository/webmail/rainloop-community-latest.zip
   or
   # https://www.rainloop.net/repository/webmail/rainloop-latest.zip   
 2) # unzip rainloop-community-latest.zip  -d /usr/share/rainloop
 3) # find /usr/share/rainloop -type d -exec chmod 755 {} \;
 4) # find /usr/share/rainloop -type f -exec chmod 644 {} \;
 5) # chown -R apache:apache /usr/share/rainloop
6a) # vi /etc/httpd/conf.d/rainloop.conf (CentOS 7/8)

#
# Rainloop Webmail is a browser-based multilingual IMAP client
#
RewriteEngine On
RewriteCond %{HTTPS} off
RewriteRule (.*) https://%{HTTP_HOST}%{REQUEST_URI}
Alias /rlmail /usr/share/rainloop
<Directory /usr/share/rainloop/>
    Options +Indexes +FollowSymLinks +ExecCGI
    AllowOverride All
    Require all granted
    #ErrorLog "/var/log/httpd/rainloop_error_log"
    #TransferLog "/var/log/httpd/rainloop_access_log"
</Directory>
<Directory /usr/share/rainloop/data/>
    Require all denied
</Directory>
6b) vi /etc/httpd/conf.d/rainloop.conf (CentOS 6)
#
# Rainloop Webmail is a browser-based multilingual IMAP client
#

RewriteEngine On
RewriteCond %{HTTPS} off
RewriteRule (.*) https://%{HTTP_HOST}%{REQUEST_URI}
Alias /rlmail /usr/share/rainloop
<Directory /usr/share/rainloop/>
  Options -Indexes
  AllowOverride All
</Directory>
<Directory /usr/share/rainloop/data>
  Order Deny,Allow
  Deny from All
</Directory>

 7) # yum -y install php-xml
 8) # systemctl restart httpd

# Configure, help
 8) https://yourserver/rlmail/?admin/
   username: admin
   password: 12345
 9) Change admin password
10) Add your domain, IMAP server, SMTP server, ...Do not use short login
11) Add contact support if needed. Requires DB support.

# Login to email account
12) https://yourserver/rlmail 
13) Additional Tutorial
14) 2-Factor Authentication