From Elendor
Once you have created and written your message and you have +PROOF'ed it to
make sure it is just how you want it, you can send it or post it by simply
pressing the hyphen key twice (--) and then hitting return. The message
will leave your buffer and go into the mailboxes of everyone on the
address and get posted to any bulletin boards on the address. There will
be a confirmation message that you have sent the message which includes a
unique ID number attached to the message. You might want to take note of
that number. You can retrieve a mail message that you have sent using the
+UNMAIL command as long as you know the message's id number and it hasn't
either disappeared from all recipient's mailboxes or been forwarded to
secondary recipients. See HELP +unmail for details.
For information on how to block +mail messages from arriving in your mailbox,
see HELP mail blocking.