Before I dig into my company's side of email transactions, I'd like to know what other people are experiencing.
As far as the time it takes from committing a change to a Jira Cloud ticket to delivery of the email notification of that change:
We have seen email delays come and go in Cloud. I believe a week ago we saw delays of hours in our Cloud instance. It impacted both Jira and Confluence. Typically it takes 5-10 minutes for native notifications to be delivered.
Depending on your delivery timelines (and core functionality needs) needs, we tend to deliver a bit faster in https://marketplace.atlassian.com/apps/1211069/notification-assistant-for-jira-email?hosting=cloud&tab=overview.
Yikes! That is certainly have normal. Mine appear within a matter of seconds to maybe a minute. Is there anything unique about your instance in your set up an email configuration? Ultimately if this is repeatable I would recommend you reach out to Atlassian support so that they could login look at your logs and see what’s going on.