address resolution problem

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Two domains.&nbsp;&nbsp;Exchange email system (domain1) attempting to reply or send to Lotus Notes (domain2) email system.<br>Lotus Notes site has no problem sending email to any email box within Exchange (domain1). However, (domain1) can not reply or send to any email box account at the Lotus Notes (domain2).<br>Upon doing a &quot;traceroute&quot; from Exchange to Lotus, it is clear that the traffic is hitting the Lotus Notes domain and the intended server, but it can not resolve to the specific email address.&nbsp;&nbsp;Three days later, it will bounce back with the Lotus Notes server generated error message stating &quot; operation timed out, message can not be delivered for 3 days&quot;. <br>I'm quite positive that it is a configuration issue within some parameter on the Lotus Notes server.&nbsp;&nbsp;This does not seem to be a Firewall or a DNS issue, but I'll be willing to entertain any ideas that you may have.<br>(Note:&nbsp;&nbsp;There is no problem sending email to any other domain or email address.&nbsp;&nbsp;The issue is specifically with this particular Lotus Notes site