> Defender will scan the entire file on opening if it's been modified
In that case it would delete the whole mailbox for EICAR. Sound plausible, but I have a WinSvr2022 machine without WinDefender (or any other AV) and Thunderbird there is slow as molasses.
But sure, if adding the path to the exclusions alleviate the problem then it's Defender causing issues.
> because opening files in windows is expensive
Yes, this is the reason I would generally advise against that. Also it mess up NTFS fragmentation bad and while nowadays it's less of an issue for a laptop with oh so fast NVMe drive in it, it's still a problem (especially if you later need to move that folder with a bazillion files in it).
In that case it would delete the whole mailbox for EICAR. Sound plausible, but I have a WinSvr2022 machine without WinDefender (or any other AV) and Thunderbird there is slow as molasses.
But sure, if adding the path to the exclusions alleviate the problem then it's Defender causing issues.
> because opening files in windows is expensive
Yes, this is the reason I would generally advise against that. Also it mess up NTFS fragmentation bad and while nowadays it's less of an issue for a laptop with oh so fast NVMe drive in it, it's still a problem (especially if you later need to move that folder with a bazillion files in it).