simple past tense and past participle of mail
"She mailed the package yesterday, but I have not yet received it."
In plain English: Mailed means sending something through the postal service so it gets delivered to someone's address.
"She mailed her application to the university last week."
Armoured in, protected by, or made of mail.
"The heavy knight's armor was not steel plate but chainmail that clinked as he marched into battle."
In plain English: Mailed means something has been sent through the postal service and is currently on its way to you.
"She received his mailed instructions via email before the meeting started."
Usage: This archaic adjective meaning armored with chainmail is rarely used in modern English and should be avoided unless writing historical fiction. Instead, use the verb form "mailed," which means to send something via postal service, for all contemporary communication contexts.
The word mailed comes from the verb mail, which means to send something by post. It entered English with that specific meaning of dispatching letters through the postal system.