I’m pretty sure not the only one getting big amounts of spam, most times with a JIRA prefix in the subject line.
Those spammers create a free cloud instance for running Jira, send their spam waves and get manually kicked of by the admins after some time.
Bad for the real clients of that cloud offer: The reputation of emails coming from any address below atlassian dot net is subzero for most spam filters. I already did read complains about valid emails not reaching others. No wonder!
I have no idea why atlassian is not reacting in a more effective way to that sort of spamming. The only way to solve it would be to kick away the own email server and rely on client provided ones. If you want to run a cloud based instance you would have to configure your smtp gateway there and everything would be fine.
It could be so simple.