I would add to Bill's suggestions a couple of points (maybe more like questions) based on your earlier comments:
- You mentioned your concern with power being a problem. If I understand you correctly, you're saying that you want Zimbra to be your main server, but to have the ISP remain as a backup. Do you mean by this that the ISP would be an alternate place for your users to check their mail, or just that the ISP would function basically to cache your email till Zimbra could come back up and haul it all down? I ask because if your users check their email on the ISP, but fail to leave it there for later download, the Zimbra box will never see it. Additionally, if they reply on the ISP, Zimbra's outbox won't get it either.
- If your Zimbra box has the same domain as your ISP-hosted email, you could run into a problem with other mail recipients who use Reverse-DNS lookup as a spam control. By this I mean that if your sent mail comes from the Zimbra box, and yet when my mail server's RDNS query returns your ISP (presumably a different IP address and maybe a different range), I'll reject the email. This may be rectified if your ISP can function as a "smarthost" and Zimbra sends all outgoing mail through that smarthost--but you'll have to get advice from others on that as I'm not familiar with the setup myself.
Quote:
Originally Posted by Rtaxerxes  So if I set a split dns up, my external DNS would point to my webhosting company's servers. Could my clients then check their mail on the external server, download it to their machine, and then it would send it to the Zimbra server and it would keep a copy? Like a cached Exchange server? |
No, you don't want to (I don't think you CAN) do it that way. Your external DNS could point to the webhosting servers, yes. But if your clients check their mail there AND DOWNLOAD IT there's no getting it back up to the Zimbra server. They need (through external accounts on Zimbra, or else with fetchmail) to download the mail TO THE ZIMBRA SERVER. As I said in #1 above, if they do a POP check to the ISP, they must be set up to "leave the message on the server" so that when Zimbra checks (presumably later) there's still a message left to download.
Having worked in Africa (tho not S.A.) myself I can sympathize with your power concerns. I'm wondering if a good UPS might not be your solution--just how intermittent is the power at your location? And for how long do you usually see it go down? A good hefty external battery connected to your UPS might just buy you enough time to keep the server up, as long as too many other things don't also get plugged into the UPS.