.PS
# mail-agents

lineht = 0.25
circlerad = 0.3

A: box "MTA"
arrow 1.5*linewid
B: box "MTA"
line
box invis "..." wid 0.5
arrow
C: box "MTA"

arrow down from C.s
D: box "MDA"
arrow right linewid/2 from D.e
E: circle "mailbox"
line <-> down from E.s
F: box "MUA"
down
box invis "recipient"


#line <- lineht+boxht/2+0.3+lineht down from A.s
line <- down 2*lineht+boxht/2+circlerad from A.s
G: box "MUA"
box invis "sender"


.PE