Isle of Man Post Office says there will be some changes to its operations over the next week because of extra traffic, more mail and closed roads.
Customers are being told there may be some disruption or delays to delivery and collection times because of the TT, although efforts will be made to try and keep them to a minimum.
On days with road closures, it may not be possible to deliver items of mail, in which case they will arrive the next day.
On days without racing, the backlog could lead to some deliveries being late.
Businesses on the course can arrange to collect their mail from local sorting offices or have it delivered to an alternative address.