@Anonymous
IMPORTANT:
Also be sure you mail each packet by a method that has tracking such as certified mail with return receipt, etc. so you'll know if and when the IRS receives the packets.
NOTE: The address at the IRS page mentioned in comments above is for a postal mailed return. In one of your comments above you mentioned "FedEx/UPS." If you plan to use a private delivery service, such as FedEx, UPS, etc., the address is different. A special street address is required. See the following page:
https://www.irs.gov/filing/submission-processing-center-street-addresses-for-private-delivery-service-pds
Also see this page about which private delivery services are acceptable:
https://www.irs.gov/filing/private-delivery-services-pds
If you plan to use one of those, ask the delivery service to give you written proof of the date of mailing.
