diff --git a/constants/item_data_constants.asm b/constants/item_data_constants.asm
index af6b8478c..faf201dda 100644
--- a/constants/item_data_constants.asm
+++ b/constants/item_data_constants.asm
@@ -59,6 +59,14 @@ DEF MAILBOX_CAPACITY      EQU 10
 DEF MAIL_STRUCT_LENGTH    EQU $2f ; mailmsg struct
 DEF MAIL_STRUCT_LENGTH_JP EQU $2a ; mailmsg_jp struct
 
+; mail languages
+	const_def
+	const MAIL_LANG_ENGLISH
+	const MAIL_LANG_FRENCH
+	const MAIL_LANG_GERMAN
+	const MAIL_LANG_ITALIAN
+	const MAIL_LANG_SPANISH
+
 ; held item effects
 	const_def
 	const HELD_NONE
diff --git a/constants/serial_constants.asm b/constants/serial_constants.asm
index 791fad245..0035071b0 100644
--- a/constants/serial_constants.asm
+++ b/constants/serial_constants.asm
@@ -30,15 +30,16 @@ DEF SERIAL_PATCH_LIST_PART_TERMINATOR EQU $ff
 ; used to replace SERIAL_NO_DATA_BYTE
 DEF SERIAL_PATCH_REPLACEMENT_BYTE     EQU $ff
 
-DEF SERIAL_PREAMBLE_LENGTH            EQU 6
-DEF SERIAL_RN_PREAMBLE_LENGTH         EQU 7
-DEF SERIAL_RNS_LENGTH                 EQU 10
+DEF SERIAL_PREAMBLE_LENGTH    EQU 6
+DEF SERIAL_RN_PREAMBLE_LENGTH EQU 7
+DEF SERIAL_RNS_LENGTH         EQU 10
 
-DEF SERIAL_MAIL_PREAMBLE_BYTE         EQU $20
-DEF SERIAL_MAIL_REPLACEMENT_BYTE      EQU $21
-DEF SERIAL_MAIL_PREAMBLE_LENGTH       EQU 5
+DEF SERIAL_MAIL_PREAMBLE_BYTE    EQU $20
+DEF SERIAL_MAIL_PREAMBLE_LENGTH  EQU 5
+; used to replace SERIAL_NO_DATA_BYTE
+DEF SERIAL_MAIL_REPLACEMENT_BYTE EQU $21
 
 ; timeout duration after exchanging a byte
-DEF SERIAL_LINK_BYTE_TIMEOUT          EQU $5000
+DEF SERIAL_LINK_BYTE_TIMEOUT EQU $5000
 
-DEF MAX_MYSTERY_GIFT_PARTNERS         EQU 5
+DEF MAX_MYSTERY_GIFT_PARTNERS EQU 5
diff --git a/engine/link/link.asm b/engine/link/link.asm
index 9998fb63f..d66b5e176 100644
--- a/engine/link/link.asm
+++ b/engine/link/link.asm
@@ -406,7 +406,7 @@ endc
 .fix_mail_loop
 	push bc
 	push de
-	farcall IsMailEuropean
+	farcall ParseMailLanguage
 	ld a, c
 	or a
 	jr z, .next
@@ -893,7 +893,7 @@ Link_PrepPartyData_Gen2:
 	ret nz
 
 ; Fill 5 bytes at wLinkPlayerMailPreamble with $20
-	ld de, wLinkPlayerMailPreamble
+	ld de, wLinkPlayerMail
 	ld a, SERIAL_MAIL_PREAMBLE_BYTE
 	call Link_CopyMailPreamble
 
@@ -911,6 +911,7 @@ Link_PrepPartyData_Gen2:
 	pop bc
 	dec b
 	jr nz, .loop2
+
 ; Copy the mail data to wLinkPlayerMailMetadata
 	ld hl, sPartyMail
 	ld b, PARTY_LENGTH
@@ -923,6 +924,8 @@ Link_PrepPartyData_Gen2:
 	pop bc
 	dec b
 	jr nz, .loop3
+
+; Translate the messages if necessary
 	ld b, PARTY_LENGTH
 	ld de, sPartyMail
 	ld hl, wLinkPlayerMailMessages
@@ -931,17 +934,17 @@ Link_PrepPartyData_Gen2:
 	push hl
 	push de
 	push hl
-	farcall IsMailEuropean
+	farcall ParseMailLanguage
 	pop de
 	ld a, c
-	or a
+	or a ; MAIL_LANG_ENGLISH
 	jr z, .next
-	sub $3
+	sub MAIL_LANG_ITALIAN
 	jr nc, .italian_spanish
 	farcall ConvertFrenchGermanMailToEnglish
 	jr .next
 .italian_spanish
-	cp $2
+	cp (MAIL_LANG_SPANISH + 1) - MAIL_LANG_ITALIAN
 	jr nc, .next
 	farcall ConvertSpanishItalianMailToEnglish
 .next
@@ -958,6 +961,7 @@ Link_PrepPartyData_Gen2:
 	jr nz, .loop4
 	call CloseSRAM
 
+; The SERIAL_NO_DATA_BYTE value isn't allowed anywhere in message text
 	ld hl, wLinkPlayerMailMessages
 	ld bc, (MAIL_MSG_LENGTH + 1) * PARTY_LENGTH
 .loop5
@@ -972,6 +976,7 @@ Link_PrepPartyData_Gen2:
 	or c
 	jr nz, .loop5
 
+; Calculate the patch offsets for the mail metadata
 	ld hl, wLinkPlayerMailMetadata
 	ld de, wLinkPlayerMailPatchSet
 	ld b, (MAIL_STRUCT_LENGTH - (MAIL_MSG_LENGTH + 1)) * PARTY_LENGTH
diff --git a/engine/pokemon/european_mail.asm b/engine/pokemon/european_mail.asm
index 2ba5e6c97..85b7a2649 100644
--- a/engine/pokemon/european_mail.asm
+++ b/engine/pokemon/european_mail.asm
@@ -1,29 +1,24 @@
-IsMailEuropean:
-; return 1 if French
-; return 2 if German
-; return 3 if Italian
-; return 4 if Spanish
-; return 0 if none of the above
-	ld c, $0
+ParseMailLanguage:
+	ld c, MAIL_LANG_ENGLISH
 	ld hl, sPartyMon1MailNationality - sPartyMon1Mail
 	add hl, de
 	ld a, [hli]
 	cp "E"
 	ret nz
 	ld a, [hli]
-	inc c
+	inc c ; MAIL_LANG_FRENCH
 	cp "F"
 	ret z
-	inc c
+	inc c ; MAIL_LANG_GERMAN
 	cp "G"
 	ret z
-	inc c
+	inc c ; MAIL_LANG_ITALIAN
 	cp "I"
 	ret z
-	inc c
+	inc c ; MAIL_LANG_SPANISH
 	cp "S"
 	ret z
-	ld c, $0
+	ld c, MAIL_LANG_ENGLISH
 	ret
 
 ; The regular font.
diff --git a/engine/pokemon/mail_2.asm b/engine/pokemon/mail_2.asm
index 59c42715b..f0b870130 100644
--- a/engine/pokemon/mail_2.asm
+++ b/engine/pokemon/mail_2.asm
@@ -31,14 +31,14 @@ ReadAnyMail:
 	push de
 	ld a, BANK(sPartyMail)
 	call OpenSRAM
-	farcall IsMailEuropean
+	farcall ParseMailLanguage
 	call CloseSRAM
 	ld a, c
 	ld de, StandardEnglishFont
-	or a
+	or a ; MAIL_LANG_ENGLISH
 	jr z, .got_font
 	ld de, FrenchGermanFont
-	sub $3
+	sub MAIL_LANG_ITALIAN
 	jr c, .got_font
 	ld de, SpanishItalianFont