FedEx or DHL are probably the best for regular non valuable Items.
If your talking about higher volume (business) then you need an Importer exporter logistics company with a qualified person as classifier, this person is a specialist on classifying items (classification book is the size of two New York phone books), certain Items need certain classifications and some are prohibited as certain handcrafts and manufactured items from
Mexico can contain lead or other hazardous materials.
Mexico, United States of America and Canada are all part of North America and have an agreement NAFTA, there are people in these country's that have studied this and the laws for many years that can help you out if your looking to export product.
be very careful of what you think you can export, I know a woman that got stuck with $10,000.00 dollars in Oaxaca clay hand crafts because they contained unacceptable levels of lead, I also got stuck with a case of Chocolate's I wanted to give as gifts because there is a limit to the amount you can ship, and never try to ship alcohol even 1 bottle of tequila.
Good luck