I have really no idea how to settle this one. Our colleagues cannot send email out due to the error message below.

[Remote server replied: 550 The sending IP (xx.xx.xx.xx) is listed on https://spamrl.com as a source of viruses.]
I have gone to the spamrl website to delist our IP but for 7 days only. After 7 days, same issue occurs again.

We even check our IP in mxtoolbox but our record is clean.
Please advise if someone got a way for this. Appreciated.