> This was on an HDD. SSD would be much faster.

OT but is that right? SSDs have many advantages but sequential read isn't necessarily one of them. SSDs seek is much faster, but this is ~one file. Throughput can be much faster due to the better interfaces, but is throughput the bottleneck for this kind of search?

SSDs are usually better at sequential read as well as seeks. Depending on how outlook organizes the file (and how it gets organized in the file system) there's probably a mix of seeking and sequential reads anyway.

Good question. Property benchmarking would be required to know for sure. It's probably rare that a multi-gigabyte file would be contiguous on disk, so lots of seeking would probably be required anyway.