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ISP change and location move RRS feed

  • Question

  • Our company has recently moved locations, which prompted the change of our ISP.  For some reason, after booting everything backup, we are unable receive emails inside the domain.  We can send out from it, but we cannot receive in.  Also, our OWA has stopped working from outside as well.  Our hosting company has changed the PTR record, but we are still stuck.  This is Exchange 2007.  We have all been stumped since the end of last week.  Any information would be greatly appreciated.

    Thanks in advance.


    KC MCTS, MCP
    Monday, August 16, 2010 4:21 PM

Answers

  • Firstly you need an ISP account which provides a static IP address. Although it might be possible to get Exchange (or any SMTP server) working with a dynamic address, believe me the hassle ain't worth it. And, if the ISP can't provide a static address, then you made a bad choice. 

    On an inhouse computer, go to http://whatismyip.com and note your IP address. Now unplug your router's phone or cable line, wait a few moments and reconnect. Test again and if the IP has changed you don't have a static address. If it stays the same, good.

    Then you need to adjust your domain's A and MX records to suit the new IP address Sometimes you can do this via a Web interface, or you may be able to tell the registrar or hosting-company to make the changes.

    You need one A record which points to your own IP address. This could be mail.domainname.com. or webmail.domainname.com. or whatever you like. For example:

    mail A 123.234.123.234

    You then need to setup a MX record pointing to this hostname. (Note that an MX cannot point directly to an IP address, only to an A or CNAME record) For example:

    mail MX  1

    Where 1 is the priority (lower=first)

    Worth noting that a DNS entry with a period at the end of the name indicates a fully-qualified name. With no period, the hostname will be automatically appended to the domain-name. So,

    mail MX 1

    and

    mail.domain.com. MX 1

    are equivalent, while

    mail.domain.com MX 1

    is invalid. (reads as mail.domain.com.domain.com)

    You might also want to set-up a lower-priority (higher number) MX record pointing to a fallback account (for example an ISP's POP account) that will serve as a 'catch-all' if your server is offline. If so you will of course want to set Exchange (or another mailclient) to check this periodically.

    Next, see if any SPF record exists. this will be in the form of a text DNS record. If it does exist it will need adjusting, otherwise it will be telling recipients that your server's IP is not authorized to send mail on your behalf, which may lead to rejection.

    BTW The PTR record doesn't need to match the domain hostname, provided it points to any valid hostname that's acceptable. An invalid or missing PTR may trigger spamfilters. This only concerns outbound mail.

    Note that these changes will take several hours to propagate around the Internet. During this time some DNS servers may see the old settings, some the new.

    Hope this helps. Internet Domain (as opposed to AD domain) setup is something of a black art but once you understand it, it's fairly straightforward. What I've described is not the only setup, for example you could find that your mail is proxied via the ISP's SMTP relay. The arrangement detailed above is the default and generally the best, though.

     

    • Proposed as answer by Elvis Wei Tuesday, August 17, 2010 11:00 AM
    • Marked as answer by Elvis Wei Tuesday, August 24, 2010 2:27 AM
    Monday, August 16, 2010 6:39 PM
  • Hi,

     

    For the inbound SMTP email, you also could run a test in the following site:

     

    https://www.testexchangeconnectivity.com/

     

    It will guide you some general steps for troubleshooting.

     

    Thanks,

     

    Elvis

     

     

    • Marked as answer by Elvis Wei Tuesday, August 24, 2010 2:27 AM
    Tuesday, August 17, 2010 11:02 AM

All replies

  • Firstly you need an ISP account which provides a static IP address. Although it might be possible to get Exchange (or any SMTP server) working with a dynamic address, believe me the hassle ain't worth it. And, if the ISP can't provide a static address, then you made a bad choice. 

    On an inhouse computer, go to http://whatismyip.com and note your IP address. Now unplug your router's phone or cable line, wait a few moments and reconnect. Test again and if the IP has changed you don't have a static address. If it stays the same, good.

    Then you need to adjust your domain's A and MX records to suit the new IP address Sometimes you can do this via a Web interface, or you may be able to tell the registrar or hosting-company to make the changes.

    You need one A record which points to your own IP address. This could be mail.domainname.com. or webmail.domainname.com. or whatever you like. For example:

    mail A 123.234.123.234

    You then need to setup a MX record pointing to this hostname. (Note that an MX cannot point directly to an IP address, only to an A or CNAME record) For example:

    mail MX  1

    Where 1 is the priority (lower=first)

    Worth noting that a DNS entry with a period at the end of the name indicates a fully-qualified name. With no period, the hostname will be automatically appended to the domain-name. So,

    mail MX 1

    and

    mail.domain.com. MX 1

    are equivalent, while

    mail.domain.com MX 1

    is invalid. (reads as mail.domain.com.domain.com)

    You might also want to set-up a lower-priority (higher number) MX record pointing to a fallback account (for example an ISP's POP account) that will serve as a 'catch-all' if your server is offline. If so you will of course want to set Exchange (or another mailclient) to check this periodically.

    Next, see if any SPF record exists. this will be in the form of a text DNS record. If it does exist it will need adjusting, otherwise it will be telling recipients that your server's IP is not authorized to send mail on your behalf, which may lead to rejection.

    BTW The PTR record doesn't need to match the domain hostname, provided it points to any valid hostname that's acceptable. An invalid or missing PTR may trigger spamfilters. This only concerns outbound mail.

    Note that these changes will take several hours to propagate around the Internet. During this time some DNS servers may see the old settings, some the new.

    Hope this helps. Internet Domain (as opposed to AD domain) setup is something of a black art but once you understand it, it's fairly straightforward. What I've described is not the only setup, for example you could find that your mail is proxied via the ISP's SMTP relay. The arrangement detailed above is the default and generally the best, though.

     

    • Proposed as answer by Elvis Wei Tuesday, August 17, 2010 11:00 AM
    • Marked as answer by Elvis Wei Tuesday, August 24, 2010 2:27 AM
    Monday, August 16, 2010 6:39 PM
  • We had to have our hosting company change the record again because they were given the wrong IP address (I was off by one number).  Hopefully tomorrow morning will be much smoother.

    KC MCTS, MCP
    Monday, August 16, 2010 7:13 PM
  • Hi,

     

    For the inbound SMTP email, you also could run a test in the following site:

     

    https://www.testexchangeconnectivity.com/

     

    It will guide you some general steps for troubleshooting.

     

    Thanks,

     

    Elvis

     

     

    • Marked as answer by Elvis Wei Tuesday, August 24, 2010 2:27 AM
    Tuesday, August 17, 2010 11:02 AM
  • Hi,

    How things are going? Any update on the issue?

    Thanks,

    Elvis

    Friday, August 20, 2010 7:03 AM
  • Yes, we have had this problem resolved.  I apologize for not posting that sooner, but things became even more hectic after wards.  There was something that needed to be changed on our firewall.  Thanks for the assistance.

    KC MCTS, MCP
    Wednesday, August 25, 2010 12:41 PM