We have seen there are some of our users that are not recieving email notifications and saw in other issues (JSDCLOUD - 7933) that it could be solved by removing blocks/bounces from atlassian side (our domain is barcelohr.atlassian.net)
I saw the workarround is to ask to Jira Support to do that because is something we cannot do by our side.
Can you check a remove the block/bounces? Thanks in advance. Regards!