[IP block (is an error, Some days they block them and other days they don't. )]

Good morning
Thank you very much for your time,

I inform you, that IP is the one that appears in the log file generated by my mail server. The client reported to me that he was sending me emails 
and I checked and I didn't have them in my inbox. When I check that log file to see what is happening, this appears:

Feb 27 09:41:34 Service unavailable; Client host [40.107.94.90] blocked using bl.spamcop.net; Blocked  - see https://www.spamcop.net/bl.shtml?40.107.94.90; from=<xxxxx@dynamowl.com> to=<xxxxxxxxx@aea.com.ar>

[IP block (is an error, Some days they block them and other days they don't. )]

Hi, I'm Luis

Plz there is an IP listed in your blacklist and I need to whitelist , the IP is 40.107.94.90.

is an error, Some days they block them and other days they don't. 

We work with them and now it is impossible to exchange emails

Thanks in advance 

Please reply to me, it's an urgent situation