diff --git a/collects/net/scribblings/sendmail.scrbl b/collects/net/scribblings/sendmail.scrbl
index cef43caa42..d034f15662 100644
--- a/collects/net/scribblings/sendmail.scrbl
+++ b/collects/net/scribblings/sendmail.scrbl
@@ -63,6 +63,10 @@ Raised when no mail recipients were specified for
 
 @section{Sendmail Unit}
 
+@margin-note{@racket[sendmail@] and @racket[sendmail^] are deprecated.
+They exist for backward-compatibility and will likely be removed in
+the future. New code should use the @racketmodname[net/sendmail] module.}
+
 @defmodule[net/sendmail-unit]
 
 @defthing[sendmail@ unit?]{
diff --git a/collects/net/sendmail.rkt b/collects/net/sendmail.rkt
index e759519616..025aec0454 100644
--- a/collects/net/sendmail.rkt
+++ b/collects/net/sendmail.rkt
@@ -1,6 +1,120 @@
 #lang racket/base
-(require racket/unit "sendmail-sig.rkt" "sendmail-unit.rkt")
 
-(define-values/invoke-unit/infer sendmail@)
+(require racket/system)
 
-(provide-signature-elements sendmail^)
+(provide send-mail-message/port
+         send-mail-message
+         (struct-out no-mail-recipients))
+
+(define-struct (no-mail-recipients exn) ())
+
+(define sendmail-search-path
+  '("/usr/lib" "/usr/sbin"))
+
+(define sendmail-program-file
+  (if (or (eq? (system-type) 'unix)
+          (eq? (system-type) 'macosx))
+    (let loop ([paths sendmail-search-path])
+      (if (null? paths)
+        (raise (make-exn:fail:unsupported
+                "unable to find sendmail on this Unix variant"
+                (current-continuation-marks)))
+        (let ([p (build-path (car paths) "sendmail")])
+          (if (and (file-exists? p)
+                   (memq 'execute (file-or-directory-permissions p)))
+            p
+            (loop (cdr paths))))))
+    (raise (make-exn:fail:unsupported
+            "sendmail only available under Unix"
+            (current-continuation-marks)))))
+
+;; send-mail-message/port :
+;; string x string x list (string) x list (string) x list (string)
+;;   [x list (string)] -> oport
+
+;; -- sender can be anything, though spoofing is not recommended.
+;; The recipients must all be pure email addresses.  Note that
+;; everything is expected to follow RFC conventions.  If any other
+;; headers are specified, they are expected to be completely
+;; formatted already.  Clients are urged to use close-output-port on
+;; the port returned by this procedure as soon as the necessary text
+;; has been written, so that the sendmail process can complete.
+
+(define (send-mail-message/port
+         sender subject to-recipients cc-recipients bcc-recipients
+         . other-headers)
+  (when (and (null? to-recipients) (null? cc-recipients)
+             (null? bcc-recipients))
+    (raise (make-no-mail-recipients
+            "no mail recipients were specified"
+            (current-continuation-marks))))
+  (let ([return (apply process* sendmail-program-file "-i"
+                       (append to-recipients cc-recipients bcc-recipients))])
+    (let ([reader (car return)]
+          [writer (cadr return)]
+          [pid (caddr return)]
+          [error-reader (cadddr return)])
+      (close-input-port reader)
+      (close-input-port error-reader)
+      (fprintf writer "From: ~a\n" sender)
+      (letrec ([write-recipient-header
+                (lambda (header-string recipients)
+                  (let ([header-space
+                         (+ (string-length header-string) 2)])
+                    (fprintf writer "~a: " header-string)
+                    (let loop ([to recipients] [indent header-space])
+                      (if (null? to)
+                        (newline writer)
+                        (let ([first (car to)]
+                              [rest (cdr to)])
+                          (let ([len (string-length first)])
+                            (if (>= (+ len indent) 80)
+                              (begin
+                                (fprintf writer
+                                         (if (null? rest)
+                                           "\n    ~a"
+                                           "\n    ~a, ")
+                                         first)
+                                (loop (cdr to)
+                                      (+ len header-space 2)))
+                              (begin
+                                (fprintf writer
+                                         (if (null? rest)
+                                           "~a "
+                                           "~a, ")
+                                         first)
+                                (loop (cdr to)
+                                      (+ len indent 2))))))))))])
+        (write-recipient-header "To" to-recipients)
+        (unless (null? cc-recipients)
+          (write-recipient-header "CC" cc-recipients)))
+      (fprintf writer "Subject: ~a\n" subject)
+      (fprintf writer "X-Mailer: Racket (racket-lang.org)\n")
+      (for-each (lambda (s)
+                  (display s writer)
+                  (newline writer))
+                other-headers)
+      (newline writer)
+      writer)))
+
+;; send-mail-message :
+;; string x string x list (string) x list (string) x list (string) x
+;;   list (string) [x list (string)] -> ()
+
+;; -- sender can be anything, though spoofing is not recommended.  The
+;; recipients must all be pure email addresses.  The text is expected
+;; to be pre-formatted.  Note that everything is expected to follow
+;; RFC conventions.  If any other headers are specified, they are
+;; expected to be completely formatted already.
+
+(define (send-mail-message
+         sender subject to-recipients cc-recipients bcc-recipients text
+         . other-headers)
+  (let ([writer (apply send-mail-message/port sender subject
+                       to-recipients cc-recipients bcc-recipients
+                       other-headers)])
+    (for-each (lambda (s)
+                (display s writer)      ; We use -i, so "." is not a problem
+                (newline writer))
+              text)
+    (close-output-port writer)))