1. We checked the source code, and we can confirm that there is no way to replace SPACE with a DOT.
There is also no way to skip addresses with spaces.
MNE uses a parameter called FilterAddressReplacementChar to replace invalid chars when it builds O365 addresses
but SPACE is always replaced by UNDERSCORE, it is not controlled by FilterAddressReplacementChar.
Historically, FilterAddressReplacementChar was added in previous versions like 4.7.x
2. We have decided to log this feature/change as an enhancement.
The product enhancement ID is TSF00728129.
This enhancement will be added to next release(s).