Thank you so much for helping me. Here is the /etc/nginx/nginx.conf file: user www-data; worker_processes 4; pid /run/nginx.pid;

events { worker_connections 768; # multi_accept on; }

http {

    ##
    # Basic Settings
    ##

    sendfile on;
    tcp_nopush on;
    tcp_nodelay on;
    keepalive_timeout 65;
    types_hash_max_size 2048;
    # server_tokens off;

    # server_names_hash_bucket_size 64;
    # server_name_in_redirect off;

    include /etc/nginx/mime.types;
    default_type application/octet-stream;

    ##
    # Logging Settings
    ##

    access_log /var/log/nginx/access.log;
    error_log /var/log/nginx/error.log;

    ##
    # Gzip Settings
    ##

    gzip on;
    gzip_disable "msie6";

    # gzip_vary on;
    # gzip_proxied any;
    # gzip_comp_level 6;
    # gzip_buffers 16 8k;
    # gzip_http_version 1.1;
    # gzip_types text/plain text/css application/json application/x-javascript text/xml application/xml application/xml$

## # nginx-naxsi config ## # Uncomment it if you installed nginx-naxsi ##

    #include /etc/nginx/naxsi_core.rules;

    ##
    # nginx-passenger config
    ##
    # Uncomment it if you installed nginx-passenger
    ##

    #passenger_root /usr;
    #passenger_ruby /usr/bin/ruby;

    ##
    # Virtual Host Configs
    ##

    include /etc/nginx/conf.d/*.conf;
    include /etc/nginx/sites-enabled/*;

}

mail {

# See sample authentication script at:

# http://wiki.nginx.org/ImapAuthenticateWithApachePhpScript

# auth_http localhost/auth.php;

# pop3_capabilities "TOP" "USER";

# imap_capabilities "IMAP4rev1" "UIDPLUS";

server {

listen localhost:110;

protocol pop3;

proxy on;

}

server {

listen localhost:143;

protocol imap;

proxy on;

}

}