error sending email with several emails

[gjgcastillo]

Hello
I have a problem with roundcube 0.7.2, when a email is send to several recipients (5 or more) with a sizeable attachment, take long time and the roundcube does nothing, no show message "Send succesful", by clicking Submit again or save draft, its show "internal server". BUT the email is sent ok, in the sent folder the email is there, and the recipients the email in recipients is ok. The problem is no response to user when send the email and no back to the mailbox. 

Greetings

[SKaero]

Whats in your error log?

[gjgcastillo]

Nothing, everything is normal. in fact, the emails have been sent, the only problem is that no response to the user that emails have been sent.
I think the problem is the long time that send email with many recipients and big attachment and the script is stopped before all emails have been sent.
I do not know if he's related to the values ​​"max_execution_time = 30" and "max_input_time = 60" (from php.ini). I don't know the optimal settings for roundcube

[SKaero]

If there is a internal server error (500) there should be an entity in the error log. How big is the attachment your trying to send?