Just found out that it is not possible to send emails with attachments larger than approx 10Mb using Roundcube. I've checked /usr/local/cpanel/3rdparty/etc/php.ini and /usr/local/cpanel/3rdparty/etc/roundcube/php.ini - both files has quite high limits, 50Mb for max_post. I tried increasing memory_limit to 256Mb, but this did not help. Roundcube is displaying message "Sending email.." for quite long time, then message disappears and nothing is being sent.

Does anyone has any idea or solution?

Thank you,
Anton.