Your alert is being triggered by over 100 emails (101) in the past hour from the qq.com domain (note that all the user-names before the @ are just random numbers) being received by your server for delivery to your email user [email protected]
In the sample you posted - the mails are being sent from the IP 184.108.40.206
which is reported to be in China, and which may not necessarily have anything to do with the qq.com domain, the sender domain is trivial to spoof.
It is likely that a script is running on, or through, the server or device that is using the IP 220.127.116.11.
This device may be a genuine mail-server that has been compromised by a script, or that has had an email account compromised, or it may be any device connected to the internet that is being levered for bulk mail, either knowingly, or because it has been exploited.
There is little you can do other than to block all mails from qq.com and/or from the IP that you are seeing. However, the spammers usually rapidly change both their IP's and their spoofed domains, so you may be chasing them for some time !
The recommended way to limit the impact of this type of spam (which is almost email ddos) is to enable greylisting to eliminate non genuine mail-servers from getting through, and by configuring your CSF to suit your hardware environment and your clients. You may want to adjust the CSF configuration Relay Tracking section to trigger on a lower setting and to block for longer periods. If you do change settings, monitor the results carefully to ensure you are not getting too many false positives that block genuine mail senders.
Take note that the default setting for CSF 'Relay' is to NOT block incoming mails, but rather to just send you an alert that something unusual is happening.
Remember that bulk spam you receive because some user somewhere had their email account, server, or device hacked or compromised (however they achieved it) is a constant reminder to you to ensure both you, and your clients, follow best practices and set passwords that are non dictionary, nor trivial to guess.