OX Guard checks common size limitations (uploadFileSizeLimitPerFile, uploadFileSizeLimit, and MAX_UPLOAD_SIZE) before encrypting emails and email attachments.

For regular users, OX Guard checks that the complete size of an E-Mail does not exceed the uploadFileSizeLimit value configured for the user, where 0 means infinity and a negative value leads to a fallback to MAX_UPLOAD_SIZE defined in server.properties.
OX Guard checks that the size of each attachment does not exceed the uploadFileSizeLimitPerFile value configured for the user, where 0 or a negative value means infinity.

For guest users, OX Guard does check the MAX_UPLOAD_SIZE defined in server.proerties.