what does email_cache used for? what is the logic?

hello
I have about 8 email addresses that imports emails into cases with different folders id.

I flushed email_cache table yesterday since it contained data more than 1 years old.

this morning I have 383 entries in the table again, the older one dating Feb 29th…

Evidently I do not know why this table is used for and it’s purpose…

Could someone explain why an entry would be added to this table?

Thank you
Serge