diff --git a/usr.bin/mail/collect.c b/usr.bin/mail/collect.c
--- a/usr.bin/mail/collect.c
+++ b/usr.bin/mail/collect.c
@@ -152,7 +152,7 @@
 	}
 	for (;;) {
 		colljmp_p = 1;
-		c = readline(stdin, linebuf, LINESIZE);
+		c = readline(stdin, linebuf, sizeof(linebuf));
 		colljmp_p = 0;
 		if (c < 0) {
 			if (value("interactive") != NULL &&
@@ -163,7 +163,7 @@
 			break;
 		}
 		lastlong = longline;
-		longline = c == LINESIZE - 1;
+		longline = c == sizeof(linebuf) - 1;
 		eofcount = 0;
 		hadintr = 0;
 		if (linebuf[0] == '.' && linebuf[1] == '\0' &&
@@ -384,11 +384,12 @@
 			(void)fflush(stdout);
 			lc = 0;
 			cc = 0;
-			while ((rc = readline(fbuf, linebuf, LINESIZE)) >= 0) {
-				if (rc != LINESIZE - 1)
+			while ((rc = readline(fbuf, linebuf,
+			    sizeof(linebuf))) >= 0) {
+				if (rc != sizeof(linebuf) - 1)
 					lc++;
 				if ((t = putline(collf, linebuf,
-					 rc != LINESIZE - 1)) < 0) {
+					 rc != sizeof(linebuf) - 1)) < 0) {
 					(void)Fclose(fbuf);
 					goto err;
 				}
diff --git a/usr.bin/mail/lex.c b/usr.bin/mail/lex.c
--- a/usr.bin/mail/lex.c
+++ b/usr.bin/mail/lex.c
@@ -223,7 +223,8 @@
 		 */
 		n = 0;
 		for (;;) {
-			if (readline(input, &linebuf[n], LINESIZE - n) < 0) {
+			if (readline(input, &linebuf[n],
+			    sizeof(linebuf) - n) < 0) {
 				if (n == 0)
 					n = -1;
 				break;
diff --git a/usr.bin/mail/util.c b/usr.bin/mail/util.c
--- a/usr.bin/mail/util.c
+++ b/usr.bin/mail/util.c
@@ -135,7 +135,7 @@
 	ibuf = setinput(mp);
 	if ((lc = mp->m_lines - 1) < 0)
 		return (NULL);
-	if (readline(ibuf, linebuf, LINESIZE) < 0)
+	if (readline(ibuf, linebuf, sizeof(linebuf)) < 0)
 		return (NULL);
 	while (lc > 0) {
 		if ((lc = gethfield(ibuf, linebuf, lc, &colon)) < 0)
@@ -184,7 +184,7 @@
 			ungetc(c = getc(f), f);
 			if (c != ' ' && c != '\t')
 				break;
-			if ((c = readline(f, line2, LINESIZE)) < 0)
+			if ((c = readline(f, line2, sizeof(line2))) < 0)
 				break;
 			rem--;
 			for (cp2 = line2; *cp2 == ' ' || *cp2 == '\t'; cp2++)
@@ -503,7 +503,7 @@
 		return (cp);
 	ibuf = setinput(mp);
 	namebuf[0] = '\0';
-	if (readline(ibuf, linebuf, LINESIZE) < 0)
+	if (readline(ibuf, linebuf, sizeof(linebuf)) < 0)
 		return (savestr(namebuf));
 newname:
 	for (cp = linebuf; *cp != '\0' && *cp != ' '; cp++)
@@ -512,10 +512,10 @@
 		;
 	for (cp2 = &namebuf[strlen(namebuf)];
 	    *cp != '\0' && *cp != ' ' && *cp != '\t' &&
-	    cp2 < namebuf + LINESIZE - 1;)
+	    cp2 < namebuf + sizeof(namebuf) - 1;)
 		*cp2++ = *cp++;
 	*cp2 = '\0';
-	if (readline(ibuf, linebuf, LINESIZE) < 0)
+	if (readline(ibuf, linebuf, sizeof(linebuf)) < 0)
 		return (savestr(namebuf));
 	if ((cp = strchr(linebuf, 'F')) == NULL)
 		return (savestr(namebuf));