Which shipping companies do you use?
Many fulfillment companies have multiple choices, but some only do business with one or two companies. It is always best to ask.
The fulfillment company should provide you with at least three different shipping options. If they are seasoned in the industry, then they realize that a labor strike could occur at any time with any company.
Typical choices for parcel shipments are UPS, FedEx, DHL and USPS.