I have a server with OS RHEL 6 and Apache/2.2.22, sometime I found this error in Apache error log:
[error] [client XXXXX] Timeout: nslookup("type" => "MX", "host" => "hotmail.com") at /usr/local/share/perl5/Net/Nslookup.pm line 114.
[error] [client XXXXX] Timeout: nslookup("type" => "MX", "host" => "hotmail.com") at /usr/local/share/perl5/Net/Nslookup.pm line 114.
[error] [client XXXXX] Timeout: nslookup("type" => "MX", "host" => "yahoo.com") at /usr/local/share/perl5/Net/Nslookup.pm line 114.
Is this a DNS problem?