We took over the maintenance, and the move, of a SmarterMail server for a large, privately held, corporation in Chicago a few years back. Some of their Board members had mailboxes which exceeded 90 gig - and we were made aware of that going into the project.
They have a single domain, but a very busy mail server: more than 350 users, located in 5 offices, all over the US, and they all use IMAP to connect. The management also standardized on Blackberry, but that's a whole other story . . .
We went into the project on a Thursday, gave a presentation, and walked out with the job of moving a leased server which had been rented at a facility where the facility operator had failed to pay the bill on the space and bandwidth, for several months, and the services had been shut down. They, literally, generated several thousand e-mail messages per day. Everything went through e-mail: sales, production, customer notifications, fleet loading instructions, driver's GPS routing, GPS delay notifications -- to sales, quality control, customers, accounting, billing - everything works through their SmarterMail e-mail server - and it was HARD DOWN for 24 hours. So, they contacted their very powerful attorneys who forced the hosting company to allow them to pay the hosting bill, to get the service back online.
They had no backup of their e-mail either - it was all on the vendor's server.
We started by using used IMAP to download each of the user's accounts. It was a long, arduous, project, and we weren't looking forward to the time that would take for all of the accounts but got lucky, when, in the middle of the night, on the first night of the project, we cracked the RDP password to the server on which SmarterMail was hosted. Turns out it wasn't very secure at all, and the hosting company didn't have very good protections in place, so it took some customer code about 50 minutes of banging away to break into their old server.
What took time was the ZIP of the SmarterMail files - more than 3 hours to ZIP the files, and then several hours, over a 100 meg connection, to transfer the zipped file to the new data center.
Once we unzipped the file, at the new center, we had almost 100% of what we needed, and only had to delete some of the index files, and do user logins to regenerate the indexes to recover missing e-mail.
Once we saw how large some of the user's accounts were, we went back to the management team and discussed the issues with them. They refused to even discuss it with the Board - some of whom are in their late 80s, and "will never part with any of their e-mail."
The new SmarterMail server -- I believe we moved them to version 11.X, was installed on a Windows Server 2012 server with 8 quad-core processors, 64 gig of ram and 10tb of hard drive space - in a RAID Level V configuration. (I didn't spec, or setup the hardware or server software, the customer worked with the colocation center.) It's a VPS, and gets backed up twice a day. All incoming and outgoing e-mail is now archived as well.
Everyone still runs IMAP, but the customer now has full control of the lease with the data center, and the Board members still have huge mailboxes, refusing to "clean them out."
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