>perl -ane "my ($email,$ip)=split(/:/,$F[9]); push @{$h{$email}},$ip}{print qq|$_ => |,join(qq|,|,@{$h{$_}}),qq|\n| for sort keys %h" YOUR-FILE.txt
#--- Output---
fred@example.com => 192.168.8.8
harry@example.com => 192.168.10.5
joe@example.com => 192.168.250.251,192.168.5.23,192.168.5.23
sally@example.com => 192.168.10.28