diff --git a/include/global.h b/include/global.h
index 037e09dfc..b52d14b3c 100644
--- a/include/global.h
+++ b/include/global.h
@@ -352,6 +352,14 @@ struct savefile_info {
 #define MAXMONNO 120 /* extinct monst after this number created */
 #define MHPMAX 500   /* maximum monster hp */
 
+/*
+ * Version 3.7.x has aspirations of portable file formats. We
+ * make a distinction between MAIL functionality and MAIL_STRUCTURES
+ * so that the underlying structures are consistent, whether MAIL is
+ * defined or not.
+ */
+#define MAIL_STRUCTURES
+
 /* PANICTRACE: Always defined for NH_DEVEL_STATUS != NH_STATUS_RELEASED
    but only for supported platforms. */
 #ifdef UNIX
diff --git a/src/bones.c b/src/bones.c
index b57d592a8..1e55db088 100644
--- a/src/bones.c
+++ b/src/bones.c
@@ -135,7 +135,7 @@ boolean restore;
 
             if (otmp->otyp == SLIME_MOLD) {
                 goodfruit(otmp->spe);
-#ifdef MAIL
+#ifdef MAIL_STRUCTURES
             } else if (otmp->otyp == SCR_MAIL) {
                 /* 0: delivered in-game via external event;
                    1: from bones or wishing; 2: written with marker */
diff --git a/src/dogmove.c b/src/dogmove.c
index e74c0a418..a70c9c70a 100644
--- a/src/dogmove.c
+++ b/src/dogmove.c
@@ -432,7 +432,7 @@ int udist;
     } else {
         if ((obj = g.level.objects[omx][omy]) != 0
             && !index(nofetch, obj->oclass)
-#ifdef MAIL
+#ifdef MAIL_STRUCTURES
             && obj->otyp != SCR_MAIL
 #endif
             ) {
diff --git a/src/eat.c b/src/eat.c
index abad8bf9c..85f07348f 100644
--- a/src/eat.c
+++ b/src/eat.c
@@ -2104,7 +2104,7 @@ eatspecial()
         return;
     }
     if (objects[otmp->otyp].oc_material == PAPER) {
-#ifdef MAIL
+#ifdef MAIL_STRUCTURES
         if (otmp->otyp == SCR_MAIL)
             /* no nutrition */
             pline("This junk mail is less than satisfying.");
@@ -2550,7 +2550,7 @@ doeat()
         /* oc_nutrition is usually weight anyway */
         else
             basenutrit = objects[otmp->otyp].oc_nutrition;
-#ifdef MAIL
+#ifdef MAIL_STRUCTURES
         if (otmp->otyp == SCR_MAIL) {
             basenutrit = 0;
             nodelicious = TRUE;
diff --git a/src/exper.c b/src/exper.c
index ab5a84348..73bfe9f4b 100644
--- a/src/exper.c
+++ b/src/exper.c
@@ -128,7 +128,7 @@ register int nk;
     if (mtmp->m_lev > 8)
         tmp += 50;
 
-#ifdef MAIL
+#ifdef MAIL_STRUCTURES
     /* Mail daemons put up no fight. */
     if (mtmp->data == &mons[PM_MAIL_DAEMON])
         tmp = 1;
diff --git a/src/mail.c b/src/mail.c
index 839e030a4..a6ec5ddc6 100644
--- a/src/mail.c
+++ b/src/mail.c
@@ -10,8 +10,12 @@
 # include <fcntl.h>
 # include <errno.h>
 #endif /* SIMPLE_MAIL */
+#endif /* MAIL */
+#ifdef MAIL_STRUCTURES
 #include "mail.h"
+#endif
 
+#ifdef MAIL
 /*
  * Notify user when new mail has arrived.  Idea by Merlyn Leroy.
  *
diff --git a/src/makemon.c b/src/makemon.c
index 5d74c1c96..dfe7940e4 100644
--- a/src/makemon.c
+++ b/src/makemon.c
@@ -1623,7 +1623,7 @@ int mndx, mvflagsmask, genomask;
         return FALSE;
     if (is_placeholder(ptr))
         return FALSE;
-#ifdef MAIL
+#ifdef MAIL_STRUCTURES
     /* special levels might ask for random demon type; reject this one */
     if (ptr == &mons[PM_MAIL_DAEMON])
         return FALSE;
diff --git a/src/mkobj.c b/src/mkobj.c
index 29f44a91b..54416100e 100644
--- a/src/mkobj.c
+++ b/src/mkobj.c
@@ -980,7 +980,7 @@ boolean artif;
             break;
         case POTION_CLASS: /* note: potions get some additional init below */
         case SCROLL_CLASS:
-#ifdef MAIL
+#ifdef MAIL_STRUCTURES
             if (otmp->otyp != SCR_MAIL)
 #endif
                 blessorcurse(otmp, 4);
diff --git a/src/mon.c b/src/mon.c
index fd030dbee..3edeac039 100644
--- a/src/mon.c
+++ b/src/mon.c
@@ -2038,7 +2038,7 @@ register struct monst *mtmp;
     /* if it's a (possibly polymorphed) quest leader, mark him as dead */
     if (mtmp->m_id == g.quest_status.leader_m_id)
         g.quest_status.leader_is_dead = TRUE;
-#ifdef MAIL
+#ifdef MAIL_STRUCTURES
     /* if the mail daemon dies, no more mail delivery.  -3. */
     if (tmp == PM_MAIL_DAEMON)
         g.mvitals[tmp].mvflags |= G_GENOD;
@@ -2412,7 +2412,7 @@ int xkill_flags; /* 1: suppress message, 2: suppress corpse, 4: pacifist */
     if (nocorpse || LEVEL_SPECIFIC_NOCORPSE(mdat))
         goto cleanup;
 
-#ifdef MAIL
+#ifdef MAIL_STRUCTURES
     if (mdat == &mons[PM_MAIL_DAEMON]) {
         stackobj(mksobj_at(SCR_MAIL, x, y, FALSE, FALSE));
     }
diff --git a/src/monmove.c b/src/monmove.c
index 0e805492c..3ec0afef9 100644
--- a/src/monmove.c
+++ b/src/monmove.c
@@ -925,7 +925,7 @@ register int after;
         mmoved = 0;
     }
 
-#ifdef MAIL
+#ifdef MAIL_STRUCTURES
     if (ptr == &mons[PM_MAIL_DAEMON]) {
         if (!Deaf && canseemon(mtmp))
             verbalize("I'm late!");
diff --git a/src/monst.c b/src/monst.c
index 4c798aec3..23af5d298 100644
--- a/src/monst.c
+++ b/src/monst.c
@@ -2589,7 +2589,7 @@ struct permonst _mons2[] = {
         M3_INFRAVISIBLE | M3_INFRAVISION | M3_DISPLACES, 34, HI_LORD),
     /* other demons
      */
-#ifdef MAIL
+#ifdef MAIL_STRUCTURES
     MON("mail daemon", S_DEMON, LVL(56, 24, 10, 127, 0),
         (G_NOGEN | G_NOCORPSE),
         A(NO_ATTK, NO_ATTK, NO_ATTK, NO_ATTK, NO_ATTK, NO_ATTK),
diff --git a/src/objects.c b/src/objects.c
index 984a67e3e..adb86dc80 100644
--- a/src/objects.c
+++ b/src/objects.c
@@ -876,7 +876,7 @@ SCROLL(None, "STRC PRST SKRZ KRK",  1,   0, 100), /* Czech and Slovak
                                                         tongue-twister */
     /* These must come last because they have special fixed descriptions.
      */
-#ifdef MAIL
+#ifdef MAIL_STRUCTURES
 SCROLL("mail",          "stamped",  0,   0,   0),
 #endif
 SCROLL("blank paper", "unlabeled",  0,  28,  60),
diff --git a/src/objnam.c b/src/objnam.c
index 079de1bbf..cc95bc653 100644
--- a/src/objnam.c
+++ b/src/objnam.c
@@ -1013,7 +1013,7 @@ unsigned doname_flags;
                  || ((!known || !objects[obj->otyp].oc_charged
                       || obj->oclass == ARMOR_CLASS
                       || obj->oclass == RING_CLASS)
-#ifdef MAIL
+#ifdef MAIL_STRUCTURES
                      && obj->otyp != SCR_MAIL
 #endif
                      && obj->otyp != FAKE_AMULET_OF_YENDOR
@@ -1326,7 +1326,7 @@ struct obj *otmp;
         return FALSE; /* always fully ID'd */
     /* check fundamental ID hallmarks first */
     if (!otmp->known || !otmp->dknown
-#ifdef MAIL
+#ifdef MAIL_STRUCTURES
         || (!otmp->bknown && otmp->otyp != SCR_MAIL)
 #else
         || !otmp->bknown
@@ -3861,7 +3861,7 @@ struct obj *no_wish;
     case STATUE:
         /* otmp->cobj already done in mksobj() */
         break;
-#ifdef MAIL
+#ifdef MAIL_STRUCTURES
     case SCR_MAIL:
         /* 0: delivered in-game via external event (or randomly for fake mail);
            1: from bones or wishing; 2: written with marker */
@@ -3909,7 +3909,7 @@ struct obj *no_wish;
             break;
         case FIGURINE:
             if (!(mons[mntmp].geno & G_UNIQ) && !is_human(&mons[mntmp])
-#ifdef MAIL
+#ifdef MAIL_STRUCTURES
                 && mntmp != PM_MAIL_DAEMON
 #endif
                 )
diff --git a/src/options.c b/src/options.c
index 5c18d6521..e4cc893d0 100644
--- a/src/options.c
+++ b/src/options.c
@@ -151,7 +151,7 @@ static const struct Bool_Opt {
     { "legacy", &flags.legacy, TRUE, DISP_IN_GAME },
     { "lit_corridor", &flags.lit_corridor, FALSE, SET_IN_GAME },
     { "lootabc", &flags.lootabc, FALSE, SET_IN_GAME },
-#ifdef MAIL
+#ifdef MAIL_STRUCTURES
     { "mail", &flags.biff, TRUE, SET_IN_GAME },
 #else
     { "mail", (boolean *) 0, TRUE, SET_IN_FILE },
diff --git a/src/role.c b/src/role.c
index 487999ac7..349c736b8 100644
--- a/src/role.c
+++ b/src/role.c
@@ -2084,7 +2084,7 @@ struct monst *mtmp;
         return "Aloha"; /* Hawaiian */
     case PM_VALKYRIE:
         return
-#ifdef MAIL
+#ifdef MAIL_STRUCTURES
                (mtmp && mtmp->data == &mons[PM_MAIL_DAEMON]) ? "Hallo" :
 #endif
                "Velkommen"; /* Norse */
diff --git a/src/trap.c b/src/trap.c
index dfb06a258..119589a47 100644
--- a/src/trap.c
+++ b/src/trap.c
@@ -3455,7 +3455,7 @@ struct obj *obj;
         grease_protect(obj, (char *) 0, victim);
     } else if (obj->oclass == SCROLL_CLASS && obj->otyp != SCR_BLANK_PAPER) {
         if (obj->otyp != SCR_BLANK_PAPER
-#ifdef MAIL
+#ifdef MAIL_STRUCTURES
             && obj->otyp != SCR_MAIL
 #endif
             ) {
@@ -3531,7 +3531,7 @@ boolean force;
         return ER_NOTHING;
     } else if (obj->oclass == SCROLL_CLASS) {
         if (obj->otyp == SCR_BLANK_PAPER
-#ifdef MAIL
+#ifdef MAIL_STRUCTURES
             || obj->otyp == SCR_MAIL
 #endif
            ) return 0;
diff --git a/src/write.c b/src/write.c
index be48b67b5..a21fc816c 100644
--- a/src/write.c
+++ b/src/write.c
@@ -18,7 +18,7 @@ register struct obj *otmp;
         return (10 * objects[otmp->otyp].oc_level);
 
     switch (otmp->otyp) {
-#ifdef MAIL
+#ifdef MAIL_STRUCTURES
     case SCR_MAIL:
         return 2;
 #endif
@@ -333,7 +333,7 @@ found:
     }
     new_obj->blessed = (curseval > 0);
     new_obj->cursed = (curseval < 0);
-#ifdef MAIL
+#ifdef MAIL_STRUCTURES
     if (new_obj->otyp == SCR_MAIL)
         /* 0: delivered in-game via external event (or randomly for fake mail);
            1: from bones or wishing; 2: written with marker */
diff --git a/src/zap.c b/src/zap.c
index a98ce852e..be7c85464 100644
--- a/src/zap.c
+++ b/src/zap.c
@@ -1231,7 +1231,7 @@ int mat, minwt;
             continue;
         if (obj_resists(otmp, 0, 0))
             continue; /* preserve unique objects */
-#ifdef MAIL
+#ifdef MAIL_STRUCTURES
         if (otmp->otyp == SCR_MAIL)
             continue;
 #endif
@@ -1358,7 +1358,7 @@ struct obj *obj;
 {
     long i;
 
-#ifdef MAIL
+#ifdef MAIL_STRUCTURES
     if (obj->otyp == SCR_MAIL)
         return;
 #endif
@@ -1456,7 +1456,7 @@ int id;
     /* preserve inventory letter if in inventory */
     if (obj_location == OBJ_INVENT)
         otmp->invlet = obj->invlet;
-#ifdef MAIL
+#ifdef MAIL_STRUCTURES
     /* You can't send yourself 100 mail messages and then
      * polymorph them into useful scrolls
      */
diff --git a/util/makedefs.c b/util/makedefs.c
index 953fdddd1..608491894 100644
--- a/util/makedefs.c
+++ b/util/makedefs.c
@@ -1111,7 +1111,7 @@ make_version()
     version.feature_set = (unsigned long) (0L
 /* levels and/or topology (0..4) */
 /* monsters (5..9) */
-#ifdef MAIL
+#ifdef MAIL_STRUCTURES
                                            | (1L << 6)
 #endif
 /* objects (10..14) */
@@ -1561,7 +1561,7 @@ static const char *build_opts[] = {
 #ifdef PANICLOG
     "errors and warnings log file",
 #endif
-#ifdef MAIL
+#ifdef MAIL_STRUCTURES
     "mail daemon",
 #endif
 #ifdef GNUDOS
diff --git a/win/share/tilemap.c b/win/share/tilemap.c
index 39f3d4fc3..6651332e9 100644
--- a/win/share/tilemap.c
+++ b/win/share/tilemap.c
@@ -54,7 +54,7 @@ struct conditionals {
 #ifndef CHARON /* not supported yet */
     { MON_GLYPH, PM_CROESUS, "Charon" },
 #endif
-#ifndef MAIL
+#ifndef MAIL_STRUCTURES
     { MON_GLYPH, PM_FAMINE, "mail daemon" },
 #endif
     /* commented out in monst.c at present */
@@ -69,7 +69,7 @@ struct conditionals {
 /* allow slime mold to look like slice of pizza, since we
  * don't know what a slime mold should look like when renamed anyway
  */
-#ifndef MAIL
+#ifndef MAIL_STRUCTURES
     { OBJ_GLYPH, SCR_STINKING_CLOUD + EXTRA_SCROLL_DESCR_COUNT,
       "stamped / mail" },
 #endif