Why am I not able to receive email to my AOL account sent from Outlook 2010/Exchange 2010?

(I'm assuming outbound mail from your Outlook arrives properly at other destinations, like a hotmail or a gmail account?)

This usually means that AOL is blocking the emails being sent by your company's Exchange Server. AOL is fairly strict with what mail it lets in so I find that there's more problems delivering mail to AOL than to other third party webmail like Gmail or Hotmail.

Depending on your company's configuration, their Exchange server may attempt to relay email directly, or through a smarthost. Whoever is delivering the message must do so though an IP Address that has a good reputation and isn't on any blacklists.

In any case... this is a question to direct at the IT person who administers your Exchange server. They have a server reputation problem.

AOL is one of those providers that require you have a Reverse DNS record to your mail server's IP address

I.e. mail.yourdomain.com - 1.2.3.4 - this is the normal record

You also need a reverse DNS record that says 1.2.3.4 = mail.yourdomain.com

This is normally done through your ISP(since they own the IP address)

As Frosty555 mentions the other way round this is to use a Smarthost, since they'll be trusted and have a reverse DNS record...

I went to a website CheckDNS and here is the result:

CheckDNS.NET tests mail-servers
  Domain mmpph.com has 2 mail-servers.  

  Checking mail server (PRI=10) mail.mmpph.com [63.204.100.82]  
  Mail server mail.mmpph.com[63.204.100.82] answers on port 25  
  <<< 220 SD1.sd.local Microsoft ESMTP MAIL Service ready at Tue, 21 Aug 2012 14:19:38 -0700
  >>> HELO www.checkdns.net 
  <<< 250 SD1.sd.local Hello [67.205.115.115]
  >>> MAIL FROM: <dnscheck@uniplace.com>
  <<< 250 2.1.0 Sender OK
  >>> RCPT TO: <postmaster@mmpph.com>
  <<< 250 2.1.5 Recipient OK
  >>> QUIT
 
Mail server mail.mmpph.com [63.204.100.82] accepts mail for mmpph.com  
  Checking mail server (PRI=90) mx.nethere.net [216.9.45.211]  
Mail server mx.nethere.net[216.9.45.211] answers on port 25  
  <<< 220 mx-1.nethere.net ESMTP
  >>> HELO www.checkdns.net 
  <<< 250 mx-1.nethere.net
  >>> MAIL FROM: <dnscheck@uniplace.com>
  <<< 250 2.1.0 Ok
  >>> RCPT TO: <postmaster@mmpph.com>
  <<< 421 4.7.1 Client host rejected: cannot find your reverse hostname, [67.205.115.115]
  >>> RCPT TO: <root@mmpph.com>
  Connection to mail server mx.nethere.net [216.9.45.211] timed out waiting for status 250  
  Some of your MX do not work properly

PRI=10 Server.  I believe the Exchange Server computer, sitting next to me in my office, does have reverse DNS enabled.  Buy how can I know this for sure?

PRI=90 Server is our backup in case the PRI=10 Server does down.

Your mail server IP is 63.204.100.82

Is this your WAN IP?

Reverse lookup for that IP comes back with - mail.estate-plan.com

Yes, we own 3 domains names:

estate-plan.com
mmpph.com
erisa-law.com

AT&T, our internet provider, is the one who is providing the reverse dns "mail.estate-plan.com".  It should be "mail.mmpph.com"

Yes, that is our WAN IP.

Right, well in this case that IP is reversing to mail-estate-plan.com

So sending emails from mmpph.com's server(mail.mmpph.com) means AOL will not accept - since it doesn't reverse to the same address

So you need to get the reverse lookup changed, I assume you don't have emails at estate-plan.com or the erisa-law.com?

Yes,  I do get e-mails at estate-plan.com, erisa-law.com and mmpph.com.

I need the reverse DNS to resolve to all 3:  

estate-plan.com
erisa-law.com
mmpph.com

How do I setup a smarthost?

Well you normally use your hosting providers mail host, i.e. whoever you have hosting your domains

In Exchange Management Console go into Org Config, Hub Transport - Send Connectors
Right click on your default send connector - properties
Into the Network tab
Instead of clicking the 'Use DNS' option select 'Route emails to the following Smarthost'
Click Add and enter the details of the hosts email server

Then enter the smarthost IP or FQDN
You may need to also add the Auth info(there's a button further down for this bit)

I think you can also use your ISP's mail host/server as well, forgot about those...

Here is a good link for you, plus the other way I forgot about is, you can use a smarthost 'just' for AOL

http://www.sbslinks.com/DNS_Smarthost.htm

That may be another option, to do this you'd setup a 2nd Send connector, and in the Address Space section specify *@aol.com - thus when someone emails anyone at aol.com it will use this send connector...just an alternate way(may be the simplest way to test this, least its not affecting all your users straight away...)