vrfy.1

.\"
.\"	@(#)vrfy.1              e07@nikhef.nl (Eric Wassenaar) 971114
.\"
.TH vrfy 1 "20220228"
.SH NAME
vrfy \- Verify electronic mail addresses
.SH SYNTAX
.B vrfy
[\fIoptions\fP]
[\fB\-v\fP]
\fIaddress\fP
[\fIhost\fP]
.br
.B vrfy
[\fIoptions\fP]
[\fB\-v\fP]
\fB\-f\fP
[\fIfile\fP]
[\fIhost\fP]
.br
.B vrfy
[\fIoptions\fP]
[\fB\-v\fP]
\fB\-p\fP
\fIdomain\fP
.br
.B vrfy
[\fIoptions\fP]
[\fB\-v\fP]
\fB\-T\fP
\fIdomain\fP
[\fIname\fP]
.SH DESCRIPTION
.I vrfy
is a tool to verify electronic mail addresses.
The only required parameter is the \fIaddress\fP to be verified.
The actual verification will be carried out at the remote machine
where mail to the given address would normally be delivered.
This may be a mail exchange host and not the final destination host.
If an explicit host is given as the second argument on the command line,
the specified address is verified at that machine.
.PP
The output of the program shows whether or not the address can
be handled at the contacted host. Error messages will be printed if
the address is invalid. If the address is recognized, the output
shows the remote host's notion of the (possibly translated)
address. If it represents a local user at that host, additional
information about the user may be displayed.
.PP
Note that if the address is accepted by the contacted host, but this
is not the final destination host, one still cannot be sure that the
address represents a valid recipient.
.PP
It is a handy tool to verify local mail addresses.
.br
If you have set up a .forward file, you can verify your own
address to check that the forwarding is done properly.
.br
If you specify an arbitrary name, you can check whether this
resolves to any valid recipients.
.SH "SPECIAL OPERATION MODES"
Some flags put the program in a special operation mode.
.SS "FILE MODE"
If the \fB\-f\fP option is specified, the program enters a special
file mode. The (optional) parameter is the name of a \fIfile\fP
containing electronic mail addresses, such as used for mailing lists.
Verification of all addresses present in the file is attempted.
If no filename is specified, vrfy acts as a filter and the addresses
to be verified are read from standard input.
.SS "PING MODE"
If the \fB\-p\fP option is specified, the program enters a special
ping mode. The required parameter is an electronic mail \fIdomain\fP
for which it will be verified whether the corresponding mail
exchangers are currently responding to SMTP requests.
.SS "ETRN MODE"
If the \fB\-T\fP option is specified, the program enters a special
etrn mode. The required parameter is an electronic mail \fIdomain\fP.
An ESMTP ETRN command will be delivered to its corresponding mail
exchangers. An optional \fIname\fP is used as the ETRN parameter.
If not specified, the local host name is used instead.
ETRN is defined in RFC 1985, and is implemented in sendmail 8.8.
.SS "RECURSIVE MODE"
If the \fB\-L\fP\ \fIlevel\fP option is specified, the received
replies to an address verification are resursively verified up to
\fIlevel\fP levels deep. This is handy for checking mailing list
expansions, and detecting possible mail forwarding loops.
.sp
Recursion stops automatically if the reply represents a local
recipient address, or in case a forwarding loop is detected.
If the received reply is the same (modulo comments) as the address
that was asked for, the request is retried at its domain itself,
unless this was the machine we just queried, or it is not an
internet domain host.
.sp
The option \fB\-R\fP is equivalent to ``\fB\-L\fP\ \fI17\fP''.
This is the maximum hop count normally used during actual mail
relaying.  This option also implies \fB\-s\fP.
.SH OPTIONS
.TP 8
.B \-v
Sets verbose mode. Prints the action the program is going to take.
.br
If specified as \fB\-vv\fP, very verbose output is printed.
The SMTP transactions with the remote host are shown in detail.
.br
If the verbose mode level is set to 3 with \fB\-vvv\fP, the
actions taken by the remote host are shown, such as alias and
forward expansions. This can be quite amusing. The remote host
must support the SMTP VERB command for this to work.
.br
In ping mode, the verbose mode level 3 will cause an extra SMTP
command HELO to be generated.
.TP
.B \-d
Prints debugging output showing the various phases of the SMTP
connection with the remote host. This is normally not of any
interest. Also prints various messages that are otherwise shown
in very verbose mode.
.br
If specified as \fB\-dd\fP, in addition all nameserver query
transactions are shown in detail.
.br
A level 3 debug mode \fB\-ddd\fP will not make any SMTP
connections at all.
.TP
.B \-a
If multiple mail exchange hosts were found, this option will
cause the operation to be carried out at each of these hosts.
Normally only the primary mail exchanger is contacted.
.TP
.B \-l
Sets local mode for error handling. Address syntax and parsing
errors are handled entirely by the program. The default is to
pass faulty addresses to the local host to get the official
error messages.
.TP
.B \-s
Strips all comments from full address specifications, and
presents only the plain address to the remote host to be verified.
Some hosts may get confused when a multiple bracketed address is
presented. This option is implied when \fB\-R\fP is given.
.TP
.B \-e
Uses the EXPN command instead of the VRFY command. Some systems
may have different treatment for these commands, so this option
may be a possible alternative.
By sendmail V5 they are usually treated the same, but not by the
sendmail V8 versions.
In case treatment is different, the VRFY command will just show
whether the presented address is valid or not, but the EXPN command
will return alias expansions, if appropriate.
Some systems allow VRFY, but disallow EXPN for privacy reasons.
.TP
.B \-h
This option causes an SMTP HELO command to be issued to the
contacted server before subsequent commands are attempted.
Servers can be configured to refuse commands unless a HELO
command is given first.
The HELO is not issued by default, since old versions of sendmail
refuse SMTP connections originating on the same machine (i.e. if
the domain name in the HELO command is its own name).
.TP
.B \-H
Similar to the \fB\-h\fP option, but now the ESMTP EHLO command
is tried first. If the contacted server does not understand this,
the SMTP HELO command is tried next.
.TP
.B \-n
Many non-sendmail hosts do not, or incorrectly or incompletely,
implement the VRFY command. Other systems have VRFY or EXPN disabled for
privacy reasons.  This option causes \fBvrfy\fP to send all of the
regular EHLO|HELO, MAIL, RCPT and RSET commands, e.g. \fB\-H\fP and
\fB\-r\fP are both implied.  Recursive mode is not possible, and will be
disabled.
.TP
.BI \-S " sender"
Defines an explicit envelope sender address to be used in the MAIL
command during the alternative protocol suite, to overrule the
default empty sender address ``<>''.
This option implies \fB\-n\fP.
.TP
.BI \-c " secs"
Sets a connect timeout value to override the default timeout of 6
seconds. This may be necessary if it takes considerable time to
connect to the remote host.
.TP
.BI \-t " secs"
Sets a read timeout value to override the default timeout of 60
seconds. This may be necessary if it takes considerable time for
the remote host to assemble all addresses in long mailing lists.
.SH "DEFAULT OPTIONS"
Default options and parameters can be preset in an environment
variable \fBVRFY_DEFAULTS\fP using the same syntax as on the command
line. They will be evaluated before the command line arguments.
.SH DIAGNOSTICS
.I vrfy
sets up an SMTP connection with the remote host where the
verifying is to be carried out.
SMTP is the TCP/IP protocol for electronic mail exchange.
.sp
If the given host does not speak SMTP, the error message
"Connection refused" is printed.
.sp
If the SMTP protocol is blocked, a "Host is unreachable"
message is printed.
.sp
If the remote host doesn't respond in time, you will get
a "Connection timed out" message.
.sp
The remote host must support the SMTP VRFY command for
doing the verification. If not, a "Command not implemented"
is printed.
.SH STRATEGY
The following strategy is used to find the remote host where
the verification is to be carried out.
.TP 4
.B a.
If an explicit verification host is specified, that host
is contacted unconditionally.
.TP
.B b.
If the address to be verified has no domain part after an '@' sign,
it is supposed to be a local recipient and will be verified at the
local host.
.TP
.B c.
If the address contains a domain part after an '@' sign, mail
exchange hosts will be fetched for that domain. If no such mail
exchangers are found, the domain part is supposed to represent
a specific host, and that host itself will be contacted.
.TP
.B d.
If mail exchangers were found, the verification will be carried
out at the primary mail exchange host.
.TP
.B e.
If the \fB\-a\fP option was given, and multiple mail exchangers
exist, the verification is also carried out at all other
mail exchange hosts.
.TP
.B f.
For the pseudo domains ".uucp" and ".bitnet" a specific server
can be compiled-in. The default is to contact the local host.
.TP
.B g.
If no mail exchangers were found for an unqualified single
hostname, the local host is contacted by default. The actual
meaning of such addresses depend on your local strategy.
.SH ENVIRONMENT
Environment variables can be used to overrule several
compiled-in defaults.
.SS VRFY_LOCALHOST
This is your nearest host running the sendmail daemon.
It is contacted in case local addresses without a domain are given.
Also (unless the \fB\-l\fP is given) when domain parsing errors were
encountered, assuming that this host can give a more appropriate
error message.
The default value is \fBlocalhost\fP.
.SS VRFY_UUCPRELAY
This host is contacted when a .uucp address is specified.
You probably won't get much useful information.
The default value is \fBlocalhost\fP.
.SS VRFY_BITNETRELAY
This host is contacted when a .bitnet or .earn address is specified.
You probably won't get much useful information.
The default value is \fBlocalhost\fP.
.SS VRFY_SINGLERELAY
This host is contacted when a single unqualified host name
could not be resolved to a fully qualified MX domain host.
It is assumed that single hosts in your own domain can be
resolved, i.e. they have an MX record.
It depends on your local strategy for unqualified hosts what they
mean: a .uucp host, a .bitnet host, or just a local host without MX.
The default value is \fBlocalhost\fP.
.SH LIMITATIONS
Some hosts have a lousy VRFY handling. Sometimes the command
is not implemented at all. Other hosts are willing to verify
only local recipients. The \fP\-n\fB option may be necessary.
.sp
Other servers may refuse the VRFY command for privacy reasons.
.sp
If the verification is not performed at the final destination
host, one cannot be sure that the given address is valid.
.SH "MAILING LISTS"
Note the following subtle differences if you want to check
an existing mailing list \fIlist\fP.
Suppose that ``\fIlist\fP\-users'' is the local alias to include
the actual file ``/mail/lists/\fIlist\fP\-users'' with recipients.
.sp
The command ``vrfy\ \fIlist\fP\-users'' will verify the proper
expansion of the mailing list at the local host. No remote
hosts are contacted to verify addresses.
.sp
The command ``vrfy\ \-f\ /mail/lists/\fIlist\fP\-users'' will verify
each individual address at the appropriate remote hosts.
.sp
The same effect can be reached when you give the command
``vrfy\ \-L\ 1\ \fIlist\fP\-users''. Use a higher recursion level
if you want to see further expansion of the mailing list.
.SH AUTHOR
Eric Wassenaar, Nikhef-H, <e07@nikhef.nl>
Greg A. Woods; Planix, Inc.; <woods@planix.ca>