Migrating to Zimbra 5.0GA with minimal downtime?

[Miklos Kalman]

Hi,

I currently have a Debian server setup with Exim4 and Dovecot which handles mail for 7 domains. Currently mail is pumped into the local mailboxes, so if a user "a" exists then all mail to a@domain1.com a@domain2.com...etc get delivered into his mailbox, also I have multiple aliases setup. I also want to reduce the user count for specific domains, so user "a" can get mail to a@domain1 and a@domain2 but not a@domain3...etc

I looked at the online demo and found that Zimbra is an amazing product and want to install it on a new server I am setting up. I will be using Zimbra 5.0GA on Ubuntu 6.06 LTS

I have the following questions/worries regarding the migration:
1/ I need to migrate ALL mailboxes and folders to the new Zimbra server along with the passwords
2/ Need to accept and send mail for ALL of the previous domains
3/ Need to do this with minimal downtime of mail services

If I modify the MX records of the domains while Zimbra is not setup correctly incoming mail will be lost (since they will be pointing to a new IP). How can I overcome this issue and join the ever growing satisfied user base of Zimbra?

I am setting it up locally before it is moved to the sever room, so no real IP will be present only once it makes it into production.

For the migration I read about imapsync, however I think using the brute force approach of downloading to Thunderbird clients and copying back to the server the most reliable, unless I am mistaken.

Please help me on this topic,

Thanks.
Miklos

[phoenix]

Welcome to the forums.

The solution with the least impact or downtime would be a Split Domain, you could move users as required. Does that not do what you require?

[Miklos Kalman]

Hi,

Thanks. So if I setup Zimbra as a secondary mailserver then it will install and once I have everything configured and synced then I can change it to the primary one?


I have three questions regarding this:
1/
What DNS entries do I need to accomplish this? Just adding a higher MX number on each domain?

2/
How do I switch zimbra back to be the primary once its done?

3/
If the "test" machine has an internal IP behind a cable modem using DHCP how can I actually verify that everything is working? Adding the dynamic IP to the ISP's domain takes ages to update and the IP might change before that I read somewhere that people are using DynDNS for this, would that help me in this case?


Also the hostname is mail.domain.com in both cases, so in case of Zimbra this should be changed as well, but once its migrated it has to be changed back (where would that be modified?)

Thanks.
Miklos

[dijichi2]

I think you're misunderstanding what mx priorities are used for. Do NOT setup your new zimbra server as a secondary with lower mx priority. Do not point mx at all to it.

Migrate your data over using imapsync - it's much more reliable than thunderbird method for various reasons. Test your new zimbra server. Test it again. Test it a third time. All the meanwhile emails are still coming into your existing dovecot server.

When your'e 150% happy the new zimbra server is running correctly:
1) Do a final imapsync
2) Switch the external IP mapping to the new zimbra server.

That's it, no MX changes necessary. If you want to be really safe during the transition, for instance while you do the final imapsync, it's a good idea to block port 25, 110, 143 to stop the data changing. Make sure your users aren't logged in while you're doing this. Might be a good idea to firewall the old server entirely except 143 to the new server, so just allow imapsync.

[Miklos Kalman]

Hi,

But isn't a valid MX record required to "fully" test the new server? I mean I want to be sure it can send and receive before deploying it completely.

I was thinking of taking one of the least least populated domains we have and setting it up with that (changing the MX to the router's IP), then imapsync ALL messages, test mail send/receive and then modify the config so it takes the major domain name (by this I mean we have company.com, company.eu company.hu ...etc) we now use company.com, but still get emails to the .eu domain, although only to its info email address. All of these are currently pumped into the user's mailboxes. If I take the company.eu and set the MX to the "testing" server's IP, install Zimbra, sync, try send and receive and add the rest as domains using the admin gui, then if all goes well rename the major domain to .com and deploy. Would this work? How would I change the default domain in zimbra once its setup and would this affect the mailbox contents that got synced?

Miklos

[dijichi2]

that's a good plan yes, use an inactive or (very!) lightly used domain for testing. one thing, don't create the other domains in Zimbra yet, otherwise any emails sent to those domains will not be delivered correctly (as in, they'll be delivered to the zimbra accounts not the live accounts).

[mmorse]

Originally Posted by Miklos Kalman

If I take the company.eu and set the MX to the "testing" server's IP, install Zimbra, sync, try send and receive and add the rest as domains using the admin gui, then if all goes well rename the major domain to .com and deploy. Would this work? How would I change the default domain in zimbra once its setup and would this affect the mailbox contents that got synced?

When you're imapsyncing, the mails themselves still retain the original sender addresses of domain.com on the inside, you're just changing the account name.
(& you can do that as many times as you wish.)

zmprov renameDomain domain.eu domain.com

And to make it easier to login with 'user' instead of typing 'user@domain.com':
zmprov mcf zimbraDefaultDomainName domain.com
You could also use a virtual host to browse to webmail.domain.com or whatever you wish and not have to type the @domain.com part of the login.

One of your comments earlier that I just wanted to hit on:

Originally Posted by Miklos Kalman

Also the hostname is mail.domain.com in both cases, so in case of Zimbra this should be changed as well, but once its migrated it has to be changed back (where would that be modified?)

You might pick a hostname to start with and avoid changing it - there's a process to do so but it's way easier if you don't have to...see: ZmSetServerName - Zimbra :: Wiki
You're currently using mail.domain.com - so to avoid conflicts you could perhaps use mailserver.domain.com or something.
(During your testing don't forget to adjust mx records for domain.eu to reflect this.)
Using the same name is ok if each individual box can resolve a different IP when querying mail.domain.com, but I don't know your DNS setup.

[Miklos Kalman]

Well I decided to go with the "least used domain" approach. I set up Zimbra using one of them. I must say I was really pleased with what I got. However I had trouble with sending mail. I was able to receive by adding the MX to my testing IP and forwarding the ports on the router. However when I tried sending mail with the client I got an email coming back:

unable to look up host XXXXX: Name or service
not known

where XXXX is an actual domain, which exists since that's where the current mail is. Is this normal? I am a bit cautious maybe too much, however I want to explore all aspects before actually moving it to production.


Another question, although not regarding the installation: is there a way to change the display for 12hour to 24hour inside zimbra? Since I am used to the 24 hour display format and its a bit annoying seeing the 12 hour format.

Miklos

[dijichi2]

on your zimbra server, see if you can 'dig xxx.xxx' that it is complaining about. look at your /etc/resolv.conf and ensure the first nameserver listed resolves correctly, both internally and externally.

[Miklos Kalman]

yep, when I issue the dig XXXX on the machine with zimbra on it, it returns correctly:

; <<>> DiG 9.3.2 <<>> XXXX.eu
;; global options: printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 47020
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 0

;; QUESTION SECTION:
;XXXXX.eu. IN A

;; AUTHORITY SECTION:
XXXXX.eu. 10800 IN SOA ans0.t-online.hu. domain.tiszanet.hu. 2007092801 28800 3600 604800 86400

;; Query time: 93 msec
;; SERVER: 195.228.240.249#53(195.228.240.249)
;; WHEN: Mon Dec 31 00:53:39 2007
;; MSG SIZE rcvd: 97

So there must be something else wrong right? The machine I am testing with is on a dynamic IP, with refreshed happening only 24 hours, so that should not be a problem. I can get email so sending should resolve successfully right?

Also resolv conf is setup to the ISP's DNS servers, which resolve correctly. The domains are actually registered by them as well, so most definitely the problem is not there.

Btw: If I add the host as an SMTP server from my thunderbird client I am able to send email to anyone without emails bouncing back.

Maybe a config error?

Miklos