When submitting from the newsletter (mailinglistAdmin.php3?action=newsletter) on a server with php running in safe mode a warning is echoed (actually time_limit is set to 10 seconds on my host).
Warning: Cannot set time limit in safe mode in /home/user/l/i/t/littllutin/www/MailingList.class on line 428
This is as issue as a few hosts I've tried before are running php in safe mode and I guess there are a lot more.
1) set error_reporting to 0 (dummy solution)
2) use autorefresh on the template and a timeout counter in the php code to send to a predefined number users
Use time() during the batch process to calculate processing time and generate some html code in the page before it times out so it will refresh itself on a url like this :
$users would be the number of mails sent during the last batch and $pos the id of the next user after the last from the current batch.