Webmail shows 504 Gateway Time-out or 502 Bad Gateway

Symptoms

• Performing some operations after being logged into webmail (or being unable to log into webmail at all) results in one of the following errors:

  504 Gateway Time-out
  502 Bad Gateway

  When importing a mailbox via webmail service, the following error is shown in the browser console:

  Failed to load resource: the server responded with a status of 504 ()

  Connection Error (Failed to reach the server)!

• The Nginx log file /var/log/nginx/error.log contains error messages that are similar to the following:

  CONFIG_TEXT: 2023/01/07 11:32:42 [error] 12026#0: *1721 upstream timed out (110: Connection timed out) while reading response header from upstream, client: 203.0.113.2, server: webmail.example.com, request: "POST /services/ajax.php/imp/viewPort HTTP/1.1", upstream: "http://203.0.113.1:7080/services/ajax.php/imp/viewPort", host: "webmail.example.com", referrer: "http://webmail.example.com/imp/dynamic.php?page=mailbox"

  CONFIG_TEXT: 2024/03/01 11:32:42 [error] 3156232#0: *6740627 upstream prematurely closed connection while reading response header from upstream, client: 203.0.113.2, server: webmail.example.com, request: "POST /roundcube/?_task=login HTTP/2.0", upstream: "https://203.0.113.1:7081/roundcube/?_task=login", host: "webmail.example.com", referrer: "https://webmail.example.com/roundcube/?_task=login&_err=session"

  CONFIG_TEXT: 2024/03/01 11:32:43 [error] 3156232#0: *6738941 connect() failed (111: Connection refused) while connecting to upstream, client: 203.0.113.2, server: webmail.example.com, request: "POST /?_task=mail&_action=refresh HTTP/2.0", upstream: "https://203.0.113.1:7081/?_task=mail&_action=refresh", host: "webmail.example.com", referrer: "https://webmail.example.com/?_task=mail&_mbox=INBOX"

• A check on the FcgidIOTimeout value in the Apache config file /etc/httpd/conf.d/fcgid.conf or (/etc/apache2/mods-enabled/fcgid.conf) provides a result that is similar to to the following:
  

  # grep FcgidIOTimeout /etc/httpd/conf.d/fcgid.conf
  FcgidIOTimeout 45

  # grep FcgidIOTimeout /etc/apache2/mods-enabled/fcgid.conf
  FcgidIOTimeout 45

• A check on the max_input_time and max_execution_time values in the webmail client configuration files provides results that are similar to the following:
  

  For Horde: /etc/psa-webmail/horde/horde/php.ini

  # egrep "max_execution_time|max_input_time" /etc/psa-webmail/horde/horde/php.ini
  max_input_time = 60
  max_execution_time = 30

  For RoundCube: /etc/psa-webmail/roundcube/php.ini

  # egrep "max_execution_time|max_input_time" /etc/psa-webmail/roundcube/php.ini
  max_input_time = 60
  max_execution_time = 30

  For Plesk Premium Mail: /usr/local/psa/var/modules/kolab/webmail/php.ini

  # egrep "max_execution_time|max_input_time" /usr/local/psa/var/modules/kolab/webmail/php.ini
  max_input_time = 60
  max_execution_time = 30

Cause

Insufficient timeout values are configured in the web server configuration files and/or within the webmail client configuration files and therefore bigger requests that require more time to be executed are timing out.

Resolution