RFC 5322
quoted-pair
ccontent
dtext
qcontent
quoted-string
word
obs-local-part
local-part
addr-spec
mailbox
received-token
id-left
msg-id
phrase
angle-addr
path
mailbox-list
address
resent-sender
sender
group-list
from
resent-from
group
address-list
bcc
cc
reply-to
resent-bcc
resent-cc
obs-resent-rply
field
name-addr
return
received
obs-received
in-reply-to
message-id
references
resent-mid
obs-phrase-list
keywords
comment
CFWS
atom
date
date-time
day-of-week
domain-literal
obs-route
time
orig-date
resent-date
obs-domain
id-right
domain
atext
dot-atom-text
RECURSE
ctext
obs-FWS
FWS
unstructured
zone
optional
subject
comments
qtext
resent-to
to
obs-utext