Problems from 193.109.254.0/23

Hello,

We receive emails from ts.fujitsu.com to momalogitech.com. in our Linux server cp426.webempresa.eu

When the emails come from 195.245.231.0/23 arrive in few minutes but when they come from 195.245.231 they always have important delays, about 8 hours...

We tried to sniff the traffic before the firewall and we didn't detect any connection to our pot 25 from that network before the emails arrive.

Could you bring some light to this issue?

Regards