PHOENIX -- Beginning May 1, people corresponding with any of Maricopa County's nearly ten-thousand jail inmates will be able to do so with postcards only.

Sheriff Joe Arpaio -- citing safety and security concerns, as well as manpower and money issues -- said inmates no longer will be allowed to receive personal letters in sealed envelopes.

Only pre-metered postcards will be allowed to reach inmates.

Postcards with adhesive stamps will be returned to the sender after May 1, as will correspondence in envelopes.

"As the inmate population continues to escalate we have to look for ways to ensure the security of the jails," Arpaio said. "Sealed envelopes have been found to contain hand cuff keys, tobacco, drugs such as heroin and methamphetamine as well as pornographic images of all kinds. We can stop nearly all of it simply by shifting to postcards."

Arapio says the only mail that won't be affected by the new policy will be legal mail.

"Another safety issue we face with sealed letters is the ease with which inmates can conduct their criminal enterprises outside the jails through the U.S. mail," Arpaio said. "Now it will be much harder to conduct any criminal business on a postcard."

Inmates in Maricopa County jails have had to correspond via postcards only since 2002.

Here are some of the postcards already in circulation for the inmates to use: