Você tem um firewall mal configurado que silenciosamente descarta todos os pacotes SYN para a porta 587. Compare a saída de um traceroute à porta 80 com um para a porta 587:
# traceroute -n -T -p 587 -q 1 -f 14 -m 20 192.0.78.24
traceroute to 192.0.78.24 (192.0.78.24), 20 hops max, 60 byte packets
14 213.155.133.22 30.492 ms
15 80.91.249.88 25.303 ms
16 62.115.116.160 30.121 ms
17 *
18 *
19 *
20 *
# traceroute -n -T -p 80 -q 1 -f 14 -m 20 192.0.78.24
traceroute to 192.0.78.24 (192.0.78.24), 20 hops max, 60 byte packets
14 62.115.112.55 29.235 ms
15 213.155.134.117 29.376 ms
16 62.115.116.158 34.012 ms
17 62.115.46.38 33.967 ms
18 192.0.78.24 33.546 ms