How can I resolve the problem if SPAM does not send from my server anymore?
The best way is to contact providers to remove your server from their blacklists. For example Spamhaus.org
Also you can redirect outgoing SMTP traffic to another IP by following this KB article:
or you can redirect by using iptables, for example:
-A PREROUTING -i eth1 -d <Blaclisted_IP>/32 -p tcp --dport 80 -j DNAT --to-destination <Not_blacklisted_IP>:3535 -A POSTROUTING -j MASQUERADE
Note: refer to Internet resources if another MTA is used on the server. For example for Sendmail: Controlling SMTP Relaying