Change MX record


We recently bought a company and are looking to move their mail gateway to our firewall (theirs lets loads of spam through).

Curently their MX record is

and we have

If I update their MX record to be identical to our will trip any spam flag etc...
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As I cannot judge your spam solution, the first thought is, it should work. As long as you configured everything in your path to accept that email (probably with TO:
Maybe test it first on a third site (your home connection), with telnet commands to, simulating emails to
After receiving seems to be no problem, adjust the mx records.
Daniel HelgenbergerCommented:
Please be careful with updating the MX.
Do test this on a weekend/holiday where not so many people are depend on their email!

I strongly recommend a well planed and timely executed mailsystem move from company1 to company2. This process is highly depended on the mail systems you use and the number of mailboxes to move. Exchange offers may ways to do this.
Changing the MX for a domain is the last step you take after everything is well tested.

That said and to answer the question:
you can change the MX of course. It will not trip any spam, since only the server which handles incoming mail changes. You would set the MX of to Be careful and check for possible SPF records and do not forget to change them as well!

But your needs to be able to handle
- you need to configure the relay domain in your mailsystem as well as all the mail boxes for compnay1 of course;
- If you have a static internal connection to the in your, then you can also create a forwarder to your old mail server for this domain; this way you would not have to move mailboxes.

If you do a firewall based spam filtering the best way with the smalest impact would be to use a free pubic IP from your as new mail ip for and then use a NAT port forward on your firewall in comany2 to (through your site to site VPN, if your comanys are not in the same place).

I highly recommend a well planed timely executed mailsystem move from company1 to company2. This process is highly depended on the mail systems you use and the number of mailboxes to move. There, chaning the MX for a domain is the last in many steps.
SteveIT ManagerCommented:
Make sure that the recipient email server that the MX record is point to and indeed any firewall/security system is configured for the incoming traffic.

Changes to MX records are usually done over a weekend, just in case, with real-world updates taking 2-24 hours.

As soon as you change them mail will stop and start gradually flowing to the new IP range you configure..

Triple check config, planning and informing users of potential down time is key to a successful change.
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detox1978Author Commented:
Thanks for the feedback.

We are using IBM Notes, so I know the email server and mail gateway will accept the emails for both email domains.

I was unsure if there would be any issues sending mail if the domain name did not matching the MX record domain (i.e. will have an mx record of

We are looking to make the change on Tuesday.

The TTL is 60 minutes.  Does this mean once I make the change everyone will have the updated details within 60 minutes?
Daniel HelgenbergerCommented:
You can set any mail server to be a domain's MX. It is entirely dependent on this mail server if it can handle the incoming domain. To my knowledge this is common practice (huge mail providers do serve thousands of domains with two or thee MX).

As for the replication, you are right - it is entirely deplend on your TTL. Worldwide distribution may take a little longer but not much.
My practice is to lower the TTL prior to an update (the old record) and change it back to a higher value when I modify / update the record.

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detox1978Author Commented:
UPdated the MX record of company1 to company2 and everything worked with any hitches.

Many thanks.
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