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ISP Changes - Seeking assistance

By GraffPM ·
I have posted this a few other places but haven't received an answer yet...

Due to family needs (small family business) I am now the System Admin for our company. This is not my normal job function so I am learning as I go. Not the best idea, I know, but we have no other choice at this time. I WISH I could hire a consultant.

So..I am asking for your help here. We are in the process of changing ISPs. In order for our email to work (using exchange 2003 on SBS Premium) what will I need to change...update? Will I need to contact the company our name is registered with? I am just not sure what steps I need to take when we receive our new static IP.

Thanks!

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All Answers

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Anyone...

by GraffPM In reply to ISP Changes - Seeking ass ...

have any thoughts on this?

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Does your exchange server ...

by Churdoo In reply to ISP Changes - Seeking ass ...

... receive the email directly via SMTP, or does it use the POP connector to POP from external mailboxes? Will both connections be live for an overlapping period of time? Is your exchange server behind a SOHO router which is port forwarding SMTP (25) to your exchange server's internal IP? Since you have SBS Premium, are you using the ISA component of SBS Prem?

If your exchange server takes direct delivery of your email via SMTP, then there are MX records in your email domain's public DNS zone, pointing to the external IP addy of the exchange server.

When your ISP cutover happens, and your IP addy changes, then you'll have to update the MX record accordingly with the new IP addy. Only problem is, that this change, due to DNS caching can take 24 hours or more for sending email servers to recognize the change and to deliver to the new addy.

If your exchange server also sends SMTP directly to recipient mail servers, and you have REVERSE DNS setup now, you'll want your new ISP to setup a reverse DNS (PTR) record for your new exchange public IP. This will cut down the chance of your email being rejected by a receiving email servers as spam.

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SMTP

by GraffPM In reply to Does your exchange server ...

All mail is delivered via SMTP. Both connections will be live since we are keeping the old DSL line for a backup. We are not behind a SOHO router. Yes, we are using ISA 2004.

I am reading up on MX records at this time..I think that is the area I am a bit confused on. All the DNS issues. Where do I update the MX records? Our site is hosted by another company so I am unsure about all the NS items as well.

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DNS Stuff

by Churdoo In reply to SMTP

There are some good DNS tools and articles on this site:
http://dnsstuff.com

MX records are what tells the world where to deliver your email. Chances are that your www host is also hosting your public DNS, so they will have to do the MX record updates, or they may have a control panel that you can use to make your own updates.

To find out for sure, go to your domain registration and see what is listed for NAMESERVERS. Whoever owns the nameservers listed on your domain reg, is your DNS host, and that is where the MX record changes need to be made. To see your domain reg, one way is to use the WHOIS lookup tool on the above site; enter your domain name to see the registration info (the tool may just link you to your registrar WHOIS and you may have to repeat the lookup there).

In your case, a couple of days before your new circuit is in place, and you know the IP that will be assigned to your exchange server, I would create an A-record and backup MX record (higher preference number than the existing MX) for the new IP. This will prime DNS with that IP since DNS changes can take days to propogate, due to caching. Once the new circuit is live and tested, I would swap the priorities of your MX records. This should result in a seamless transition of your email delivery without a loss or delay of a single message. Since you're leaving the current circuit in place as a backup, then I would leave that IP as a backup MX (higher preference number), and in the event that you need to, fallback to that IP should be automatic.

Caution, if you are not sure what you're doing with your public DNS, STOP! and find out for sure before you make a change. Errors in your public DNS can take down services, and fixing errors can sometimes take a day or days to propogate. I'm not trying to scare you, because it's not really that hard once you understand it, but this is the reality of the situation.

Hope this is helpful.
--C

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Start

by retro77 In reply to ISP Changes - Seeking ass ...

Start with pricing out the ISP and deciding if thats the one you want. Have your curcuit installed and get your new IP from your new ISP.

Then find out who is hosting your DNS. You can use a whois tool to do this:
http://www.networksolutions.com/whois/index.jsp

Then you have to contact them or login the account via the internet to change the IP to your new one. Change the DNS to your new one. The replication can take a couple days so do this on a Friday night.

Make sure your router or ISA server is configured on that new curcuit and you should be good to go.

There are tons of small steps in the above, but that is the big picture.

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Thanks

by GraffPM In reply to Start

for the info. I realize you only gave me the big picture...could you point me in the right direction for reading up on the tons of small steps? Any websites that are very informative?

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