SymptomsClient logged in the Horde webmail interface with mail account. But 'Inbox' button is missed under the 'Mail' button.
ResolutionMake sure that php function 'pack' is not disabled in php configuration.
Some php functions can be disabled. It can be done by modifying values of the directive 'disable_functions' in php.ini file.
Please check that function 'pack' is not listed in the output of the command:
grep -i disable_functions /etc/php.ini /etc/php.d/* /usr/local/etc/php.ini
If this function is disabled, please exclude it from the disabled functions list and restart apache after modification. Then check if button is 'Inbox' is available.
Additional informationAnother disabled php functions can also affect on the horde webmail functionality. If horde webmail does not work as it should, please disable directive 'disable_functions' in php.ini, restart apache and check horde webmail functionality. If horde webmail functionality is improved, it is necessary to determine which function affects it. It can be done by disabling each function one-by-one. Once it is found, please exclude it from disabled functions list.