OpenBCM can handle up to 16 mail flags, at the moment only 6 are used:

1. (Mail-)Type:
   defines mail type
   "A"  Acknoledge mail
   "B"  Bulletin mail
   "P"  Personal mail
   "T"  National Traffic Services

2. (FWD-)Hold:
   defines if mail is on hold status and therefor can't be forwarded to
   other BBS
   "!"  mail will be forwarded (=hold flag not set)
   "B"  S&F partner doesn't support binary mails
   "E"  mails has errors (e.g. a BID is missing)
   "F"  erased after forward, mail is not forwarded again
   "F"  mail on hold, because S&F without password (reject.bcm)
   "H"  global hold status set (reject.bcm)
   "K"  S&F partner doesn't accept BIN mails
   "L"  mail loops (only user mails)
   "L"  mail on hold, because locally received (reject.bcm)
   "M"  S&F partner doesn't accept 7plus mails
   "M"  m_filter, no forward (errorlevel 2)
   "N"  No (S&F partner who don't support REJ)
   "O"  mail on hold, because no AX25/tty-password (reject.bcm)
   "P"  mail on hold, because no AX25-password (reject.bcm)
   "R"  mail was rejected by S&F partner
   "S"  size, mail is to big (if "-b" option is set in "fwd.bcm")
   "X"  set on hold by sysop
   "Z"  mail on hold, because from GUEST

3. (FWD-)Prop(osal):
   "!"  not proposed
   """  mail was proposed in forward queue and accepted with OK

4. Rep(lied):
   "!"  no reply send
   "1"  user mail was replied

5. Cont(enttype):
   contenttype of mail
   "!"  text or unknown
   "6"  bad 7plus content
   "7"  correct 7plus content
   "8"  7plus (7inf) content
   "8"  7plus (7txt) content
   "B"  AutoBIN content
   "H"  HTML content

6. Erase(info):
   "!"  not erased
   "E"  erased by user
   "S"  erased by sysop
   "W"  erase by a server (WP, Mail, Tell)
   "K"  local remote-erased
   "L"  remote-erased (from origin bbs)
   "X"  remote-erased (not from origin bbs)
   "F"  erased after forward
   "T"  erased after transfer to other board

Note: You can show the mailflags with option "-h" using READ command!