| Flag | § | Meaning |
| % | F=% | Hold delivery until ETRN or -qI or -qR or -qS (V8.10 and above) |
| | F=0 (zero) | Turn off MX lookups for delivery agent (V8.8 and above) |
| 1 | F=1 (one) | Don't send null bytes (V8.10 and above) |
| 2 | F=2 | Force SMTP even if ESMTP is offered (V8.12 and above) |
| 3 | F=3 | Extend quoted-printable to EBCDIC (V8.7 and above) |
| 5 | F=5 | Use the localaddr rule set 5 after local aliasing (V8.7 and above) |
| 6 | F=6 | Always strip headers to 7 bits (V8.10 and above) |
| 7 | F=7 | Strip the high bit when delivering (V8.6 and above) |
| 8 | F=8 | Force EightBitMode=p MIME encoding (V8.7 and above) |
| 9 | F=9 | Convert 7- to 8-bit if appropriate (V8.8 and above) |
| : | F=: ( colon ) | Check for :include: files (V8.7 and above) |
| | F= (vertical bar) | Check for program addresses (V8.7 and above) |
| / | F=/ (forward slash) | Check for /file addresses (V8.7 and above) |
| @ | F=@ | User can be User Database key (V8.7 and above) |
| a | F=a | Run extended SMTP protocol (V8.6 and above) |
| A | F=A | User can be to the LHS of an alias (V8.7 and above) |
| b | F=b | Add a blank line after message (V8.6 and above) |
| c | F=c | Exclude comment from $g in headers (V8.6 and above) |
| C | F=C | Add @domain to recipient |
| d | F=d | Never enclose route addresses in <> (V8.7 and above) |
| D | F=D | Need Date: in header |
| e | F=e | Mark expensive delivery agents |
| E | F=E | Change extra From into >From |
| f | F=f | Delivery agent adds -f to argv |
| F | F=F | Need From: in header |
| g | F=g | Suppress From:<> (V8.6 and above) |
| h | F=h | Preserve uppercase in hostname |
| H | | Reserved for Mail11v3 (preview headers) |
| i | F=i | User Database sender rewrite of envelope (V8.7 and above) |
| I | F=I (uppercase i) | Send SMTP VERB to other site (deprecated) |
| j | F=j | User Database rewrite of header recipient addresses (V8.7 and above) |
| k | F=k | Don't check for loops in EHLO command (V8.7 and above) |
| l | F=l (lowercase L) | Agent performs local (final) delivery |
| L | F=L | Specify SMTP line limits (obsolete) |
| m | F=m | Multiple recipients possible |
| M | F=M | Need Message-ID: in header |
| n | F=n | Don't use Unix-style From in header |
| N | | Reserved for Mail11v3 (returns multistatus) |
| o | F=o | Always run delivery agent as recipient (V8.7 and above) |
| p | F=p | Process return path per RFC821 (deprecated) |
| P | F=P | Need Return-Path: in header |
| q | F=q | 250 versus 252 return for SMTP VRFY (V8.8 and above) |
| r | F=r | Delivery agent adds -r to argv |
| R | F=R | Use a reserved TCP port (V8.6 and above) |
| s | F=s | Strip quotation marks |
| S | F=S | Assume specified user-id and group -id (Revised for V8.7) |
| u | F=u | Preserve uppercase for username |
| U | F=U | Use UUCP-style From line |
| v | | Reserved for SysVR4 |
| V | | Reserved for UIUC |
| w | F=w | Check for valid user identity (V8.7 and above) |
| x | F=x | Need Full- Name : in header |
| X | F=X | Delivery agent needs RFC2821 hidden dot |
| z | F=z | Deliver with LMTP (V8.9 and above) |
| Z | F=Z | Apply DialDelay option's sleep (V8.12 and above) |
| ~ | | Reserved for SGI (check for valid home directory) |
