The Notes Migrator migration log for an account contains notification lines for attachments exceeding size limits and being removed.
For example the below lines can be seen in the migration log:
BTNotesGetAttachment: Size of attachment 'abdcef.pdf' exceeds size limit (9 MB versus 5 MB limit)
This log notification is by design and refers to the large attachment processing in Notes Migrator, it is not an error notification.
The attachment is processed through a different method in these cases with the file being detached from the message during migration and then being re-attached to the resulting migrated message.
This notification does not indicate that an attachment was not migrated, only that it was treated as a large attachment and migrated outside the MIME Stream conversion.
The large attachment processing will treat embedded items such as images as attachments in Outlook if these exceed the size limit set.
These would be items such as icons in signatures or embedded images. In cases where the embedded item is lower than the size limit there will be no impact on the item and it will be migrated as it is in source.
This setting is intended to cover situations where migrations may be failing due to "Out of memory" errors during processing and also to handle cases where messages are migrated as RTF directly (eg invalid TNEF Conversions in Domino).
Note: The migration profile does have limits for maximum attachment sizes on the destination options tab. This setting is not intended to replace those limits.