Question: I am using Office Version 2206 (Build 15330.20230), the current version. When I am searching for an email it shows a message that maybe not all results are shown and that it is still indexing 127279 emails, many more emails than I have recieved since the issue occured. When I search for something it only shows results that more than a year old.

This problem occurs only since a couple of days, possibly since the last update from July 06.

Answer: 
I'd suggest that it is more a convention, less a technical issue.

[Wikipedia's page on the word size choice in computer architecture](https://en.wikipedia.org/wiki/Word_(computer_architecture)) has a nice table with a *lot* of older computer architectures with byte/word sizes which are not a power of two. On that page there is also a box in the upper right hand corner with links to individual pages for many unconventional word sizes (e.g., 12, 18, 24 but also 31, 36, 45 (!) etc.

One area where the byte/word size has significant impact is in compilers; i.e. your C compiler needs to know how many bits are available in the addressing registers (i.e. 16/24/32/64 bit), and many aspects flow from that (i.e., how arrays of integers are laid out in memory and how the code to access that is generated by the compiler).

Code built for one word size is then of course also usually incompatible with code built for other word sizes, even if the CPU in question would otherwise use exactly the same coding for their assembly language.

Also, if your data storage is binary - in the old days it was not unheard of to just dump a page of memory into a file and read that back in "as is" later - this completely breaks down if the two machines use different word sizes (even if other aspects, like [endianess](https://en.wikipedia.org/wiki/Endianness), are the same).

All of this leads to the industry converging on a smaller and smaller number of word sizes, just like many other technological aspects have converged over the years. As user alt-ctrl-delor has mentioned in his answer, one (maybe minor) aspect here could be that if you have some integer within your CPU, maybe even only internally/in hardware, where you wish to store the location of a bit within an register (i.e., a dynamic value ranging from 0 to the word size of your register), then having a register width that is a power of 2 avoids waste and some error states (i.e., addressing a bit past the non-power-of-two word size).
I think some of the arguments missing is that it is convenient that a register can be divided into two parts which are easy to work with, for instance with smaller registers. Hence, for the intel architecture, you initially had 16 bits registers that were subdivided into two 8-bit subregisters, and then these registers were extended to 32 bits, keeping the least significant digits addressable as 16 bits register, and then to 64 bits. If you had a 48 bits register, it would leave an awkward 16 most significant bits part, and you would have to play with 16 bits and 32 bits subregisters... What a pain !

Moreover, when you multiply the contents of two registers, you need a register of twice that size (or two registers of the initial size) to contain the result. Having registers that cannot be combined two by two would make things complicated for arithmetic.

I guess this view is supported by the fact that, for addressing (and not arithmetic), the processors internally use other numbers of bits.