diff --git a/usr.bin/mail/aux.c b/usr.bin/mail/aux.c
index 4db5b8506d1e..2f735b1b2723 100644
--- a/usr.bin/mail/aux.c
+++ b/usr.bin/mail/aux.c
@@ -181,7 +181,7 @@ gethfield(f, linebuf, rem, colon)
 			return (-1);
 		if ((c = readline(f, linebuf, LINESIZE)) <= 0)
 			return (-1);
-		for (cp = linebuf; isprint(*cp) && *cp != ' ' && *cp != ':';
+		for (cp = linebuf; isprint((unsigned char)*cp) && *cp != ' ' && *cp != ':';
 		    cp++)
 			;
 		if (*cp != ':' || cp == linebuf)
@@ -256,7 +256,7 @@ istrncpy(dest, src, dsize)
 
 	strlcpy(dest, src, dsize);
 	while (*dest)
-		*dest++ = tolower(*dest);
+		*dest++ = tolower((unsigned char)*dest);
 }
 
 /*
diff --git a/usr.bin/mail/cmd2.c b/usr.bin/mail/cmd2.c
index 5ab6b85a8d92..b25af303713c 100644
--- a/usr.bin/mail/cmd2.c
+++ b/usr.bin/mail/cmd2.c
@@ -249,7 +249,7 @@ snarf(linebuf, flag)
 	 * Strip away trailing blanks.
 	 */
 
-	while (cp > linebuf && isspace(*cp))
+	while (cp > linebuf && isspace((unsigned char)*cp))
 		cp--;
 	*++cp = '\0';
 
@@ -257,13 +257,13 @@ snarf(linebuf, flag)
 	 * Now search for the beginning of the file name.
 	 */
 
-	while (cp > linebuf && !isspace(*cp))
+	while (cp > linebuf && !isspace((unsigned char)*cp))
 		cp--;
 	if (*cp == '\0') {
 		printf("No file specified.\n");
 		return (NULL);
 	}
-	if (isspace(*cp))
+	if (isspace((unsigned char)*cp))
 		*cp++ = '\0';
 	else
 		*flag = 0;
diff --git a/usr.bin/mail/collect.c b/usr.bin/mail/collect.c
index 4c42c9072cb1..6fc74935b158 100644
--- a/usr.bin/mail/collect.c
+++ b/usr.bin/mail/collect.c
@@ -248,7 +248,7 @@ cont:
 			 * Set the Subject line.
 			 */
 			cp = &linebuf[2];
-			while (isspace(*cp))
+			while (isspace((unsigned char)*cp))
 				cp++;
 			hp->h_subject = savestr(cp);
 			break;
@@ -257,7 +257,7 @@ cont:
 			 * Set the Reply-To line.
 			 */
 			cp = &linebuf[2];
-			while (isspace(*cp))
+			while (isspace((unsigned char)*cp))
 				cp++;
 			hp->h_replyto = savestr(cp);
 			break;
@@ -287,7 +287,7 @@ cont:
 			 * then open it and copy the contents to collf.
 			 */
 			cp = &linebuf[2];
-			while (isspace(*cp))
+			while (isspace((unsigned char)*cp))
 				cp++;
 			if (*cp == '\0') {
 				printf("Interpolate what file?\n");
@@ -563,7 +563,7 @@ forward(ms, fp, fn, f)
 		tabst = NULL;
 	else if ((tabst = value("indentprefix")) == NULL)
 		tabst = "\t";
-	ig = isupper(f) ? NULL : ignore;
+	ig = isupper((unsigned char)f) ? NULL : ignore;
 	printf("Interpolating:");
 	for (; *msgvec != 0; msgvec++) {
 		struct message *mp = message + *msgvec - 1;
diff --git a/usr.bin/mail/edit.c b/usr.bin/mail/edit.c
index e8d54deccb54..8e5e14abcf05 100644
--- a/usr.bin/mail/edit.c
+++ b/usr.bin/mail/edit.c
@@ -115,7 +115,7 @@ edit1(msgvec, type)
 			size = ftello(otf);
 			mp->m_block = blockof(size);
 			mp->m_offset = boffsetof(size);
-			mp->m_size = fsize(fp);
+			mp->m_size = (long)fsize(fp);
 			mp->m_lines = 0;
 			mp->m_flag |= MODIFY;
 			rewind(fp);
diff --git a/usr.bin/mail/fio.c b/usr.bin/mail/fio.c
index 0c78e3eb0a88..a10021b498d5 100644
--- a/usr.bin/mail/fio.c
+++ b/usr.bin/mail/fio.c
@@ -82,15 +82,15 @@ setptr(ibuf, offset)
 		 msgCount = 0;
 	} else {
 		/* Seek into the file to get to the new messages */
-		(void)fseek(ibuf, offset, SEEK_SET);
+		(void)fseeko(ibuf, offset, SEEK_SET);
 		/*
 		 * We need to make "offset" a pointer to the end of
 		 * the temp file that has the copy of the mail file.
 		 * If any messages have been edited, this will be
 		 * different from the offset into the mail file.
 		 */
-		(void)fseek(otf, 0L, SEEK_END);
-		offset = ftell(otf);
+		(void)fseeko(otf, (off_t)0, SEEK_END);
+		offset = ftello(otf);
 	}
 	omsgCount = msgCount;
 	maybe = 1;
@@ -138,7 +138,7 @@ setptr(ibuf, offset)
 		} else if (inhead) {
 			for (cp = linebuf, cp2 = "status";; cp++) {
 				if ((c = *cp2++) == '\0') {
-					while (isspace(*cp++))
+					while (isspace((unsigned char)*cp++))
 						;
 					if (cp[-1] != ':')
 						break;
@@ -150,7 +150,7 @@ setptr(ibuf, offset)
 					inhead = 0;
 					break;
 				}
-				if (*cp != c && *cp != toupper(c))
+				if (*cp != c && *cp != toupper((unsigned char)c))
 					break;
 			}
 		}
@@ -221,7 +221,7 @@ setinput(mp)
 	(void)fflush(otf);
 	if (fseeko(itf,
 		   positionof(mp->m_block, mp->m_offset), SEEK_SET) < 0)
-		err(1, "fseek");
+		err(1, "fseeko");
 	return (itf);
 }
 
diff --git a/usr.bin/mail/head.c b/usr.bin/mail/head.c
index 806ab6dc7c12..61f43daec2c6 100644
--- a/usr.bin/mail/head.c
+++ b/usr.bin/mail/head.c
@@ -204,11 +204,11 @@ cmatch(cp, tp)
 	while (*cp != '\0' && *tp != '\0')
 		switch (*tp++) {
 		case 'a':
-			if (!islower(*cp++))
+			if (!islower((unsigned char)*cp++))
 				return (0);
 			break;
 		case 'A':
-			if (!isupper(*cp++))
+			if (!isupper((unsigned char)*cp++))
 				return (0);
 			break;
 		case ' ':
@@ -216,20 +216,20 @@ cmatch(cp, tp)
 				return (0);
 			break;
 		case '0':
-			if (!isdigit(*cp++))
+			if (!isdigit((unsigned char)*cp++))
 				return (0);
 			break;
 		case 'O':
-			if (*cp != ' ' && !isdigit(*cp))
+			if (*cp != ' ' && !isdigit((unsigned char)*cp))
 				return (0);
 			cp++;
 			break;
 		case 'p':
-			if (!ispunct(*cp++))
+			if (!ispunct((unsigned char)*cp++))
 				return (0);
 			break;
 		case 'P':
-			if (*cp != ' ' && !ispunct(*cp))
+			if (*cp != ' ' && !ispunct((unsigned char)*cp))
 				return (0);
 			cp++;
 			break;
diff --git a/usr.bin/mail/lex.c b/usr.bin/mail/lex.c
index c7f674ce7b1f..46255b8f9d56 100644
--- a/usr.bin/mail/lex.c
+++ b/usr.bin/mail/lex.c
@@ -143,7 +143,7 @@ setfile(name)
 	 * the mail file, so reset mailsize to be where
 	 * we really are in the file...
 	 */
-	mailsize = ftell(ibuf);
+	mailsize = ftello(ibuf);
 	(void)Fclose(ibuf);
 	relsesigs();
 	sawcom = 0;
@@ -162,7 +162,7 @@ nomail:
 int
 incfile()
 {
-	int newsize;
+	off_t newsize;
 	int omsgCount = msgCount;
 	FILE *ibuf;
 
@@ -179,7 +179,7 @@ incfile()
 		return (0);		/* no new mail */
 	setptr(ibuf, mailsize);
 	setmsize(msgCount);
-	mailsize = ftell(ibuf);
+	mailsize = ftello(ibuf);
 	(void)Fclose(ibuf);
 	relsesigs();
 	return (msgCount - omsgCount);
@@ -290,7 +290,7 @@ execute(linebuf, contxt)
 	 * lexical conventions.
 	 */
 
-	for (cp = linebuf; isspace(*cp); cp++)
+	for (cp = linebuf; isspace((unsigned char)*cp); cp++)
 		;
 	if (*cp == '!') {
 		if (sourcing) {
@@ -398,7 +398,7 @@ execute(linebuf, contxt)
 		 * Just the straight string, with
 		 * leading blanks removed.
 		 */
-		while (isspace(*cp))
+		while (isspace((unsigned char)*cp))
 			cp++;
 		e = (*com->c_func)(cp);
 		break;
diff --git a/usr.bin/mail/list.c b/usr.bin/mail/list.c
index 1dbc587ae174..be5df83f9f08 100644
--- a/usr.bin/mail/list.c
+++ b/usr.bin/mail/list.c
@@ -555,9 +555,9 @@ scan(sp)
 	 * Return TNUMBER when done.
 	 */
 
-	if (isdigit(c)) {
+	if (isdigit((unsigned char)c)) {
 		lexnumber = 0;
-		while (isdigit(c)) {
+		while (isdigit((unsigned char)c)) {
 			lexnumber = lexnumber*10 + c - '0';
 			*cp2++ = c;
 			c = *cp++;
@@ -678,7 +678,7 @@ matchsender(str, mesg)
 	while (*cp2 != '\0') {
 		if (*cp == '\0')
 			return (1);
-		if (toupper(*cp++) != toupper(*cp2++)) {
+		if (toupper((unsigned char)*cp++) != toupper((unsigned char)*cp2++)) {
 			cp2 = ++backup;
 			cp = str;
 		}
@@ -717,7 +717,7 @@ matchto(str, mesg)
 			while (*cp2 != '\0') {
 				if (*cp == '\0')
 					return (1);
-				if (toupper(*cp++) != toupper(*cp2++)) {
+				if (toupper((unsigned char)*cp++) != toupper((unsigned char)*cp2++)) {
 					cp2 = ++backup;
 					cp = str;
 				}
@@ -775,7 +775,7 @@ matchsubj(str, mesg)
 	while (*cp2 != '\0') {
 		if (*cp == '\0')
 			return (1);
-		if (toupper(*cp++) != toupper(*cp2++)) {
+		if (toupper((unsigned char)*cp++) != toupper((unsigned char)*cp2++)) {
 			cp2 = ++backup;
 			cp = str;
 		}
diff --git a/usr.bin/mail/send.c b/usr.bin/mail/send.c
index 58f029aea84b..7351cc55d6e6 100644
--- a/usr.bin/mail/send.c
+++ b/usr.bin/mail/send.c
@@ -123,10 +123,10 @@ sendmessage(mp, obuf, doign, prefix)
 			 * Pick up the header field if we have one.
 			 */
 			for (cp = line; (c = *cp++) != '\0' && c != ':' &&
-			    !isspace(c);)
+			    !isspace((unsigned char)c);)
 				;
 			cp2 = --cp;
-			while (isspace(*cp++))
+			while (isspace((unsigned char)*cp++))
 				;
 			if (cp[-1] != ':') {
 				/*