Visvanath Ratnaweera

Possibility: Those mails are rejected at the receiving end. To follow up, first let us know your e-mail settings:
Site administration > Plugins > Message outputs > Email > SMTP hosts, SMTP security, SMTP username, SMTP password and
Site administration > Server > Support contact > Support e-mail. (Of course you need to annonymize sufficiently!)

Then read the mail box of the support contact. Are there bounced mail?

If not send mail from from a PHP script outside Moodle or using pure "telnet" to an invalid address and see whether the support mailbox get them bounced.

BTW, how is Postfix configured: myorigin? myhostname? relayhost? Search for the e-mail of the missing recepients in the mail log (/var/log/mail.log).

Before re-repeating the same discussion, see the post https://moodle.org/mod/forum/discuss.php?d=317841#p1274815 in the thread which I provided earlier.

The parallel discussion "Video Format supported by moodle & uploading limitation of videos" https://moodle.org/mod/forum/discuss.php?d=317841 has useful pointers. There was a wish for seperate video forum which which seems to be buried: "Wasn't there a dedicated forum for videos?" https://moodle.org/mod/forum/discuss.php?d=313462.

Probably your command line PHP interpreter is older than the Apache module. Compare "php -v" on the CLI and phpinfo according to https://docs.moodle.org/en/PHP#Displaying_phpinfo_outside_of_Moodle.

> "Insufficient memory detected"

Is that all? Doesn't say how much necessary and how much is available?

Try https://docs.moodle.org/en/PHP#Displaying_phpinfo_outside_of_Moodle to get the available value.