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DNS/Mail issue

Posted on 2010-09-03
Medium Priority
Last Modified: 2013-11-30
A small company have asked me to fix up their Exchange server since it went down some time ago.

Since this happened, they decided to start using the webmail hosting service provided by 123-Reg, who also provided them with their domain name.

They're going to want their email directed back to their static IP, of course.

In the 123-Reg control panel for that domain, their are 4 A records: @, *, mail, and www. All these point to 123-Reg's servers, with the same IP.

There is also an MX record, pointing to mail.theirdomainname.co.uk.

Is it really as simple as changing the A record for mail from the 123-Reg server address to their static IP, and that's it, or have I missed something?

Many thanks!

Question by:mprssjpr
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LVL 28

Expert Comment

ID: 33600737
First test it

enter domain name
check MX records and where it goes to > probably the webhosting company.

How to change
a) Create an A-record for - mail.theirdomainname.co.uk > with public IP
b) Create an MX-record to point to mail.theirdomainname.co.uk
It's that simple

Godaddy's guide here

Author Comment

ID: 33600909
Hey Sunnyc7, thanks for that - I'm about to give that a go.

Before I do, though - can you clear up my confusion? They already have an MX record pointing to mail.theirdomainname.co.uk.

Wouldn't changing the A record for mail.theirdomainname.co.uk to point to their static IP be enough? And leaving the mx record as is? I guess what I'm saying is, what would be the point of creating another mx record that was identical?

Sorry - DNS is NOT my strong point!
LVL 28

Assisted Solution

sunnyc7 earned 800 total points
ID: 33601165
I'd suggest if they already have that, its better you dont mess with that

You can create another record called mail2 / or mymail / or corp.theotherdomain.co.uk

Right now they will have a MX record of priority 10 / 20
What you need todo is - create a new record with a priority lower than that - like 5 so that mails will start getting delivered there.

Be warned.
The minute you change DNS - webmail will stop working, and all your emails will expect a exchange server at other end. If exchange server is not there - emails will be delivered to the MX next in line > mail.theotherdomain.co.uk

End state

5 mail2.otherdomain.co.uk > public IP > exchange
10 mail.otherdomain.co.uk > webmail.
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LVL 24

Accepted Solution

B H earned 1200 total points
ID: 33601171
all you need to do is change the A record for mail.theirdomainname.co.uk...

that gets the mail to the front door of the server...

you also need to make sure:
- port 25 is forwarded into the server
- the server accepts mail for that domain
- your users have email addresses@thatdomian.com

dont accept my answer, i'm just adding onto sunny's comment, he gets the points :)
LVL 28

Expert Comment

ID: 33601178
bryon :))
You already have a million of them...I am still playing catch-up.

I prefer not changing the existing mail.domain.co.uk
> you really dont know what gets screwed-up while changing DNS
LVL 24

Expert Comment

by:B H
ID: 33601181
o i would also add... forget webmail at the host... use outlook web access...

thus changing the A record for webmail.them.co.uk to point to the exchange server ip address, and having OWA enabled, and forwarding port 80/443 to the server too

reason is, if all the mail hits their server like it should... webmail at the host will be blank/outdated/useless

i would advise against the multiple mx records because, if your server is rebooting or otherwise down, mail WILL go to the web host and users won't have any idea how to go get that mail

LVL 28

Expert Comment

ID: 33601199
Thats true @ multiple MX.

i usually have my primary pointing to Exchange
and backup pointing to - www.mxsave.com
Thats a store forward insurance - costs $5/month
They store emails when my exchange is down for anything - and then forwards it back when exchange is back up.

Bryon has a point about multiple MX.

My concern is
a) I am really not sure if exchange is configured properly at other end before we change MX.
Usually thats the last step in installation.

MPRSSJPR > Please confirm if exchange is good to go, before you swap MX.

Author Comment

ID: 33601284
Guys - thanks - this is really helpful.

The main point I want to clear up is that the current domain for the mx record is exactly the same as the one that the exchange server will be receiving, i.e. it is NOW mail.theirdomainname.co.uk, and I want to keep it as that, just send it somewhere else.

So, I guess Bryon answered my question?  "all you need to do is change the A record for mail.theirdomainname.co.uk..."

What I thought about just changing the A record seems right - thanks. Please correct me if I've misunderstood that. And can someone please just double, double confirm that there's no problem with leaving that mx record there, as is? I don't have to delete it THEN recreate it exactly the same, or something weird like that?

Sunnyc7 - sadly, Exchange isn't going to be good to go when I do the change - I've got 48 hours to do the job, and they're gonna need their mail working when they come back to work on monday. I'm gonna do the change first thing in the morning, so by the time I've backed up the server, wiped it, and got it going again, I might have some mail coming in on Sunday. I've explained that they might lose some mail, but they don't expect to receive much over the weekend, so they're ok about it.

I'm pretty confident that Exchange will be fine - I'm pretty experienced with it, and having just installed Server 2008 with Exchange 2010 at my main office, this old SBS is going to be, if you'll excuse the expression, a p*ss in the park.

Also, thanks for the tip about mxsave.com - I'll check that out for my company.

Thanks again for the help, guys - much appreciated.
LVL 28

Expert Comment

ID: 33601297
I suggest - change the MX on Saturday night after you are done with this - and give it 24 hrs to propagate.
or do it sunday afternoon.

Changing mx first without having a exchange to get going = little risky.

will wait for bryon's thoughts.
LVL 24

Expert Comment

by:B H
ID: 33601625
well, mail right now is going to the web host - so changing the mx record (or A record) will go like this:

- people who didnt cache the result will send mail directly to exchange
- people who did cache it will still send mail to the host anyway

you can always circle back and get the stray mail from the host manually

you can also set the TTL on the mx and A records right now, to like 30 minutes, that'll help propagation in the future

if the host is willing to work with you, you can tell them to redirect any incoming mail to your server...any decent host can do that for you in 5 minutes
LVL 24

Expert Comment

by:B H
ID: 33601627
- people who did cache it will still send mail to the host anyway - until the current TTL expires and they re-lookup the new entries

usually we tell clients that takes 48 hours but in most cases it only takes 12 or so

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