I have a client that uses Outlook as the e-mail client for a cloud based exchange server. His mailbox size is approaching 20 GB, with a total mail count of over 150,000. He needs to be able to access all of his e-mail from at least two computers. Outlook has some reliability issues when the OST gets this large. Specifically the search function, which he may use 20 times or more per day, provides inconsistent results. There are also other random issues that seem to be most easily corrected by reinitializing the OST file, which can take more than a day to resynchronize. I have archived some of his e-mail to PST files, and copied them to all of his computers. However, this is undesirable because it causes great confusion to the user (the company owner) to have e-mail in multiple folders located far from the inbox. However, it would be workable to have folders directly under the inbox.
This user typically has 20+ mail windows and ten applications (most with multiple open files) open at any given time. His computers all run Windows 7 64-bit and have lots of memory, so at least in theory are able to easily handle so many open applications and files.
Is there a better PC, Mac or Web based client for this extreme type of user? He needs it to be fast, reliable and easy to use.