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421 4.4.2 Connection dropped due to TimedOut.

    Question

  • We are having Exchange 2013 and all emails are comin & going fine except 1 domain.

    From this domain, we can receive the emails but when we send email to them we receive below notification.

    Diagnostic information for administrators:<o:p></o:p>

    Generating server: FQDN of my mail server
    Receiving server: FQDN of far end server (IP address
    of far end server)

    Recipeint email address
    Remote Server at FQDN and IP of far end returned '400 4.4.7 Message delayed'
    24-08-2016 07:07:58 - Remote Server at
    FQDN and IP of far end returned '441 4.4.1 Error encountered while communicating with primary target IP address: "421 4.4.2 Connection dropped due to TimedOut." Attempted failover to alternate host, but that did not succeed. Either there are no alternate hosts, or delivery failed to all alternate hosts. The last endpoint attempted was IP of far end:25'

    All emails to other domains goes well.


    Thanks, Rishi Pandit.

    Tuesday, August 30, 2016 7:05 AM

Answers

  • perhaps try and contact them and find out if they having issues, maybe a firewall is allowing and then denying the connection.

    Edward van Biljon - Exchange MVP

    Tuesday, August 30, 2016 8:11 AM
    Moderator
  • Hi Rishi,

    Find the MX record for the recipient server domain and try to telnet that from your email server on port 25 and try to send an email from DOS prompt to see if that has pass through to narrow down the issue.

    If that doesnt work there is some network connectivity issue between your and the target domain.

    Or they might have just blocked your domain??

    Can you send the email to other external domain?

    Tuesday, August 30, 2016 8:42 AM
  • Hi,

    As I mentioned above, this issue occur on destination server, and it should be troubleshooting with its administrator.

    Temporarily, we can use NSLOOKUP to verify the MX, A record for destination server, or send a test message from a public email system, for example Outlook.com account.


    Allen Wang
    TechNet Community Support


    Please remember to mark the replies as an answers if they help and unmark them if they provide no help.
    If you have feedback for TechNet Subscriber Support, contact tnmff@microsoft.com.

    Sunday, September 4, 2016 6:37 AM
    Moderator

All replies

  • Hi

    Please check if you can telnet to that domain on port 25 and ask them if they allow mail from you. Also check if you not grey/blacklisted.


    Edward van Biljon - Exchange MVP

    Tuesday, August 30, 2016 7:55 AM
    Moderator
  • Thanks Edward,

    I tried the same but telnet doesn't connect on port 25 from my mail servers. I checked on mxtoolbox & many other and found my domain is not blacklisted anywhere.


    Thanks, Rishi Pandit.


    • Edited by Rishi Pandit Tuesday, August 30, 2016 8:14 AM telnet
    Tuesday, August 30, 2016 8:10 AM
  • perhaps try and contact them and find out if they having issues, maybe a firewall is allowing and then denying the connection.

    Edward van Biljon - Exchange MVP

    Tuesday, August 30, 2016 8:11 AM
    Moderator
  • Hi Rishi,

    Find the MX record for the recipient server domain and try to telnet that from your email server on port 25 and try to send an email from DOS prompt to see if that has pass through to narrow down the issue.

    If that doesnt work there is some network connectivity issue between your and the target domain.

    Or they might have just blocked your domain??

    Can you send the email to other external domain?

    Tuesday, August 30, 2016 8:42 AM
  • Hi Rishi,

    Any updates about this issue?

    If this issue only occur on some special domain, and mail flow works fine for other domain, also I notice that we cannot telnet port 25 for this domain (we need port 25 open in firewall for inbound and outbound mail flow), I suppose that this issue's arise in destination domain and need contact its administrator for further assistance.


    Allen Wang
    TechNet Community Support


    Please remember to mark the replies as an answers if they help and unmark them if they provide no help.
    If you have feedback for TechNet Subscriber Support, contact tnmff@microsoft.com.
    Thursday, September 1, 2016 8:48 AM
    Moderator
  • I am not getting any contact details of the far end admin team. Also sent email from other domain which went successfully to them but received no response. Actually i have a pool of Public IP from isp so from all other IPs (Public) i can do a telnet 25 to their smtp server but not from mail server. There is no port blocking at our end. Cant i find by any other way and ensure my IP is blocked on their firewall ? My be this que. is for other forum and cannot be answered here But yeah in current scenario i believe that my particular public IP of mail server is falling somewhere in block range of far end firewall.

    Thanks, Rishi Pandit.

    Thursday, September 1, 2016 11:54 AM
  • Hi,

    As I mentioned above, this issue occur on destination server, and it should be troubleshooting with its administrator.

    Temporarily, we can use NSLOOKUP to verify the MX, A record for destination server, or send a test message from a public email system, for example Outlook.com account.


    Allen Wang
    TechNet Community Support


    Please remember to mark the replies as an answers if they help and unmark them if they provide no help.
    If you have feedback for TechNet Subscriber Support, contact tnmff@microsoft.com.

    Sunday, September 4, 2016 6:37 AM
    Moderator