Delayed page display

I have a script that retrieves several queued email messages from a MySQL database and sends them out, printing out progress as it goes along; for example: email1@example.com ... sent email2@example.com ... sent email3@example.com ... sent Either "sent" or "failed" is displayed based on the result of the mail() call. When accessing the script however, the browser(?) waits until the script has completely processed prior to displaying the page (instead of displaying it in progress). Other scripts on the same system display in progress, and it's unclear what's different/special about this one. The page header contains several hundred characters, and line breaks are included after each "sent", so I don't think it's a browser buffering issue. The behavior is the same in both Firefox & IE. The engine is PHP 5.2 under Apache. And none of the ob_ functions are being used. I did try adding a flush(), but the behavior is still the same. So what else could cause the page to buffer completely prior to being displayed? Any insights appreciated, Robert