General MX record question


#1

I am going to transfer my Dreamhost email accounts over to Google Apps, and am in the process of making the MX record changes.

Just as a general question, when I change the MX records, does that mean that all email will go directly to my boxes at Google, or will it first have to bounce to Dreamhost which will then tell the email to go to Google?

In other words, if I change my MX to Google and Dreamhost is down, will I still get email at Google?

Thanks for your help.


#2

The only part of DH you’ll be relying on here with this setup is their DNS. If that should go down (which is extremely uncommon), then you won’t receive new E-mails, though in such a case sending server should keep trying to put the E-mail through for about 3 days IIRC (instead of bouncing).

–Matttail
art.googlies.net - personal website


#3

This is my understanding. Please correct me if I am wrong.

Even you M record points to google app, the emails (or packages) will still come to DH first. DH’s system will check M record and forward emails (or packages) to either DH’s email server or google’s email server depending on the M record setting.

If DH’s DNS server is down, emails do not know where to go. If DH’s DNS server is up and email server is down, emails can reach DH and be forwared to google.

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#4

Patrick this is not exactly correct – mattail described it better above. You are right that Dreamhost DNS needs to be up for this to work, but the term “forward” is not quite right. The way it works is:

outgoing.example.com gets a message via smtp that is supposed to be delivered to user@yourdomain.com
outgoing.example.com looks up yourdomain.com in the root DNS system to find out what its nameservers are
outgoing.example.com contacts one of the nameservers (ie ns1.dreamhost.com) and asks for the MX record for yourdomain.com
ns1.dreamhost.com replies with the equivalent of "gmail is the mail agent for yourdomain.com, send the mail there"
outgoing.example.com directly contacts the server you specified in the MX record (ie gmail) and directly transfers the mail there. Google stores it in the correct mailbox.

So the DNS service does require dreamhost to be up, but the actual transfer of mail data does not pass through dreamhost at all.


#5

hi thanks for the tips.

actually the “forward” I mean is same as what you described.

The package will reach DH first and DH tells where is the email server for the package. DH does not forward the email but only tells where the email server is.

Is that correct? :stuck_out_tongue:

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#6

I don’t believe the above poster meant to nit pick patricktan, but just straighten out a possible misunderstanding. When you’re talking about E-mail and you say “forward” people think of one thing.

And DH isn’t really forwarding any packages along, or data, but helping the sending mail server figure out where to send the data.

–Matttail
art.googlies.net - personal website


#7

What do you mean by this?

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#8

I mean, before an email is sent, a connection must be built first. some packages are routed between soure and destination. DH’s server will route these packages to the right email server to build the connection.

Is my understanding right?

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#9

matttail wrote:

[quote]The only part of DH you’ll be relying on here with this setup is their
DNS. If that should go down (which is extremely uncommon)

[/quote]

You were saying? :wink:

MBP:~ steve$ dig @66.201.54.66 mydomain.com any
; <<>> DiG 9.3.2 <<>> @66.201.54.66 mydomain.com any
; (1 server found)
;; global options: printcmd
;; connection timed out; no servers could be reached

MBP:~ steve$ dig @66.33.206.206 mydomain.com any
; <<>> DiG 9.3.2 <<>> @66.33.206.206 mydomain.com any
; (1 server found)
;; global options: printcmd
;; connection timed out; no servers could be reached

MBP:~ steve$ dig @66.33.216.216 mydomain.com any
; <<>> DiG 9.3.2 <<>> @66.33.216.216 mydomain.com any
; (1 server found)
;; global options: printcmd
;; connection timed out; no servers could be reached