Igor, AfterLogic Support

<?php

class CDefaultValuesPlugin extends AApiPlugin
{
    /**
     * @param CApiPluginManager $oPluginManager
     */
    public function __construct(CApiPluginManager $oPluginManager)
    {
        parent::__construct('1.0', $oPluginManager);

        $this->AddHook('api-account-construct', 'PluginApiAccountConstruct');
    }

    /**
     * @param CAccount $oAccount
     */
    public function PluginApiAccountConstruct(&$oAccount)
    {
        if (is_a($oAccount, 'CAccount'))
        {
            $oAccount->MailMode =
                EAccountMailMode::KeepMessagesOnServerAndDeleteMessageWhenItsRemovedFromTrash;
        }
    }

}

return new CDefaultValuesPlugin($this);