All our servers are pre-configured to send email directly via Postfix. Postfix is what's known as an MTA (Mail Transfer Agent) so will happily send emails directly to where-ever they need to go.

However, due to abusive spammers, many IP addresses get blacklisted. Often when an IP address is blacklisted, the emails sent from that IP just get dropped (they often don't even appear in your spam folder). Because spammers often abuse services which use dynamic IP addresses (e.g. AWS servers, consumer grade internet connections, etc) they are often particularly problematic.

That means that reliably sending emails from a server with a dynamic IP address is often hit and miss (and it just depends whether the IP you are randomly assigned was recently used by a spammer).

The best way to work around that is to use a third party SMTP relay. The idea is that you send emails via a trusted third party which takes care of email deliver-ability issues. There are a range of these sort of services available, many of them free, at least for low volume usage. We did a fair bit of research around that last year and decided that we thought Sendin Blue gave the best value, if you want to give it a try, please sign up here. It has a quite generous free plan, which should be adequate for most low to medium users. The paid plans provide great value for money in our opinion, for more intensive email sending requirements.

Once you have an account, then you can use Confconsole to configure your mail relay. If you'd rather use something other than SendinBlue, then you can also use Confconsole to manually configure an alternate custom SMTP relay.

Having said that, there is a possibly that there is a bug in the Canvas appliance and it genuinely can't send emails. But my guess is that's not the case. Setting up a SMTP relay should clarify whether the issue is the emails getting generated (by Canvas) or not, or whether it's simply a matter of deliver-ability. Also, if you are sending all of your emails to the same domain (for example, school email addresses all on the one domain; e.g. name@some.school.com) perhaps there are some rules that could be adjusted locally to allow your server to send directly?

I hope that heads you in the right direction.