/// <summary>
/// Gets MX record collection.
/// Each string is a single record formatted as "Priority,Host,TTL"
/// If Null then no MX servers where found.
/// </summary>
/// <param name="domain">The domain to get MXs for.</param>
/// <returns>See description.</returns>
/// <throws>Win32 Exception. (123)</throws>
internal static string[] GetMXRecords(string domain)
{
// Pointer to the first DNS result.
IntPtr ptrFirstRecord = IntPtr.Zero;
ArrayList results = new ArrayList();
try
{
// Do the DNS query.
int retVal = dnsapi.DnsQuery_W(ref domain, QueryTypes.DNS_TYPE_MX, QueryOptions.DNS_QUERY_STANDARD, 0, ref ptrFirstRecord, 0);
// If the retVal isn't 0 then something went wrong
if (retVal != 0)
{
// There are no DNS records of type MX.
if (retVal == 9003 || retVal == 9501)
{
return(null);
}
else if (retVal == 123)
{
throw new DNSDomainNotFoundException();
}
else
{
//throw new Win32Exception(retVal);
System.Diagnostics.Trace.WriteLine("DNS_API:" + domain + " (" + retVal + ")");
return(null);
}
}
MXRecord recMx = (MXRecord)Marshal.PtrToStructure(ptrFirstRecord, typeof(MXRecord));;
IntPtr ptrCurrentRecord = IntPtr.Zero;
for (ptrCurrentRecord = ptrFirstRecord; !ptrCurrentRecord.Equals(IntPtr.Zero); ptrCurrentRecord = recMx.pNext)
{
recMx = (MXRecord)Marshal.PtrToStructure(ptrCurrentRecord, typeof(MXRecord));
if (recMx.wType == 15)
{
string line = recMx.wPreference.ToString() + "," + Marshal.PtrToStringAuto(recMx.pNameExchange) + "," + recMx.dwTtl.ToString();
results.Add(line);
}
}
}
finally
{
// Always cleanup.
DnsRecordListFree(ptrFirstRecord, 0);
}
return((string[])results.ToArray(typeof(string)));
}
/// <summary>
/// Gets an Array of MX Records for the specified domain. If none found returns null.
/// </summary>
/// <param name="domain"></param>
/// <returns></returns>
public static MXRecord[] GetMXRecords(string domain)
{
// Make sure the domain is all lower.
domain = domain.ToLower();
// This is what we'll be returning.
MXRecord[] mxRecords = null;
// Try and get DNS from internal cache.
if (DNSManager._Records.TryGetValue(domain, out mxRecords))
{
// Found cached records.
// Make sure they haven't expired.
if (mxRecords.Count((MXRecord mx) => mx.Dead) < 1)
{
return(mxRecords);
}
}
string[] records = null;
try
{
// Get the records from DNS
records = dnsapi.GetMXRecords(domain);
}
catch (DNSDomainNotFoundException)
{
// Ensure records is null.
records = null;
}
// No MX records for domain.
if (records == null)
{
// If there are no MX records use the hostname as per SMTP RFC.
MXRecord[] mxs = new MXRecord[]
{
new MXRecord(domain, 10, 300u, MxRecordSrc.A)
};
_Records.AddOrUpdate(domain, mxs, (string key, MXRecord[] existing) => mxs);
return(mxs);
}
mxRecords = new MXRecord[records.Length];
for (int i = 0; i < mxRecords.Length; i++)
{
string[] split = records[i].Split(new char[] { ',' });
if (split.Length == 3)
{
mxRecords[i] = new MXRecord(split[1], int.Parse(split[0]), uint.Parse(split[2]), MxRecordSrc.MX);
}
}
// Order by preferance
mxRecords = (
from mx in mxRecords
where mx != null
orderby mx.Preference
select mx).ToArray <MXRecord>();
DNSManager._Records.TryAdd(domain, mxRecords);
return(mxRecords);
}
