You only have one reverse dns recod and that's for the 'primary' domain which would also be the FQDN of the zimbra mail server. Your reverse dns is also likely to require your ISP to set it for you. You should also search for, and read, some of the many topics/blogs/articles on the internet which co...

As you're using the Zextras packages then there's nothing better. I would suggest you read the wiki article on the Zextras web site on how to do a 'move' to a new server.

Why don't you use a Backup MX server? You can get one at a reasonable cost or perhaps your DNS hosting service provides that as a 'feature'. My DNS hosting service is with https://easydns.com/ and they, as do many others, provide that as a free service if you host your DNS with them.

Take a look at some of the following and see if they help: https://www.startpage.com/do/dsearch?query=Access+denied.+Proxy+unable+to+reach+user+mailbox+server+%22z-push%22&cat=web&pl=opensearch&language=english I'd also suggest that you might like to post this on the z-push forum (or mai...

As you're using Activesync with the OSS version, are you using Zextras or something else to use these accounts with Zimbra?

You should always give the ZCS version when asking a question such as yours, please post the full output of the following command: zmcontrol -v You should always give a full description of the problem (and solutions you've tried). Your title states "mailbox configuration error ", is this a...

When you're asked for the ZCS version you should always provide the full output of the following command:

It was also mentioned that your DNS may not be working. Are you behind a NAT router and if so, have you setup a Split DNS configuration?

The major problem you have is that your version of ZCS is very old and has bugs a vulnerabilities that mean it could be hacked. I'd suggest you get yourself onto the most recent version of ZCS as soon as possible.

How about imapsync?

https://www.startpage.com/do/dsearch?query=imapsync+wiki+zimbra&cat=web&pl=opensearch&language=english

JonMemere wrote: Zimbra version 9 is not open source right ?

Wrong, there are two version and those are the OSS versions provided by beezim and Xextras.