This issue has been finally resolved and will be included in 1.3. To be precise on some hosting the email function always returned with an error.
Thanks to soccerki who encountered the same issue today i was finally able to reproduce the error and dig deep into the networking process.
Our ajax function uses a GET request and some environments seem to limit the length of a get parameter value.
In this case the length of the email list was above 4000 characters and his server's suhosin configuration
Code:
suhosin.get.max_value_length
only allowed 2.000.
Normally this is even lower, default value of 512. But i guess it depends on how restrictive your host is. To be honest, a length limit never even crossed my mind
So the ajax returned always with an error since the data was cutoff.
Changing the request from GET to POST seem to have corrected the issue, since post parameter value has a much higher limit.
Code:
suhosin.post.max_value_length
defaults to 65.000, so it A LOT of difference. An i would believe most hosts even higher this default value. In case of soccerki's, this value was 1.000.000, so a lot of room.
If anyone should still encounter issues, which i don't believe on the huge POST limit, we ask to open a new support thread.