DenisChenu wrote: sending it in batch dpon't change the spam issue, really no reason.

Yes, it does. Especially for learning spam filters analysing ongoing mailserver traffic. These systems tend to lower the spam threshold if lots of emails are send within short time from a certain IP. Thus, using smaller batches and sending emails every 30 minutes instead of every 2 minutes may help.

DenisChenu wrote: And if the server have some condiguration issue (for example on ISP limit email 1 by second, if you send 2 in one second : all next message is refused) then : batch can broke more sneding email.
mrli999 already said he can not use batch like that because his hoster/ISP limit sending email.

Of course it depends on the configuration details. But if there are such limits, a cronjob is a good choice because you can easily configure it to stay within the required limits e.g. by increasing the delay between the different script calls.

@DenisChenu @ Mazi Thank you very much for your help and all efforts. I really love limesurvey, it is powerful. Thanks.

Some more information:
1. This morning, I manually click the "send invitations" button. The batch size is still 60, but it send more than 60 emails. And the IE windows keep being busy. I have to interrupt the window by closing it.

2. Using SMTP in limesurvey, it will send email one by one until reach the email batch size. The ISP doesn't restrict such kind of sending behavior. The ISP doesn't allow: sending too many email in 15 minutes (no more than 700 email using the same aacount; no more than 1500 email using the samp IP).

So I hope to send the second batch of emails 15 minutes later after the first batch. That is, first batch (for example 60 emails), waiting 15 minutes, second batch (also 60 emails), waiting 15 minutes and another batch.

3. I am not a programer. As a user, I think maybe you can do as the following
a. Add another input just below the "email batch size" , it can be: Batch Interval. Here user can set the interval between two batch.
b. In the page "send email invitations", maybe can add another input: MAX emails you want to send today. And then change the now submit to "Send one batch invitations", and add another button-"Send MAX invitations"

Thanks again!

Another information:

This morning, even the batch size is 60, it will only send 35 emails every time. So I changed the batch size to 70, then it will send 45 emails. I think this problem was caused by failing email.(Most probably) .

Then I passed the value Y to ''bypassbademails" using the following code: ie.Document.getElementById("bypassbademails").Value = "Y". But it still sent only 35 emails when batch size is 60.

Can you please let me know how to reslove this problem using VBA? THANKS