My mail server stopped working this morning and found out the information store dismounted. It's a standard version and we already changed the limit to max 75 gb. I also found this in the event viewer:
Exchange store 'First Storage Group\Mailbox Store (FAIR001)': The current physical size of this database (the .edb file and the .stm file) is 76 GB. This database has exceeded the size limit of 75 GB. However, the logical free space in this database has not yet been evaluated. Therefore, it is possible that this database contains enough free space to bring its logical size below the maximum size limit.
If the logical database size exceeds the maximum size limit, it will be dismounted on a regular basis.