Use an explicit patch rather than sed (which might fail silently).

PKGBUILD

@@ -36,6 +36,7 @@ source=(
   https://de.postfix.org/ftpmirror/official/$pkgbase-$pkgver.tar.gz
   $pkgbase-$pkgver.tar.gz.sig::https://de.postfix.org/ftpmirror/official/$pkgbase-$pkgver.tar.gz.gpg2
   $pkgbase-3.5.8-main_defaults.patch
+  $pkgbase-3.9.0-mail_params.patch
   $pkgbase.service
   $pkgbase.sysusers
   $pkgbase.tmpfiles
@@ -43,12 +44,14 @@ source=(
 sha512sums=('2b227bb6b57e4cf2d727a23762b161f2328959faa4683d63b35543701c3e954be552537eaa14a899c65ec4856d9f91b0398337088a6e2b48c0446fd406be8de4'
             'SKIP'
             '4630bb84206e0534723f50e4fb0e6f83a47cfd33187801eede052962d332b2754af8761a8d2b81f52cba9d07a7a0335eef06e22347ec7bc69b86f561685bd575'
+            '6ff26a9e2330c6a930b15953c1dd7cc730318e80bef47667c0271ddb8132e64005e0d075e84d9d7a970eed789694093626ebd9053b9499333c6d526b57b0ea4c'
             '27f54747ad480d65b560c9dbc97e12c6353e4bceca0ffe3e358e31de56db0ad79928164c9f8790c73a9f791daa378253d2ee29b5a766661778553ec889b2cf97'
             'a7f15970f613ae7b98ce1b84ca0a6034ce3cc7b2b9ce7160dad9731f740fb762f4a54f44acceb5f06f8744fa9e952b088086af8a69da388a600b742a3cda37f2'
             'd08574a6acd595fc146513c92dc1bb341c3432d67de1e93ab73a7ce60e385dd34f3a55e3d3d7aec5f358ac4aae260f028599ac47650ebc663cea3043a760a7bc')
 b2sums=('eda349dbf7fe45636fbd68991dba9f099a41dd402f7d58eb71ae881b5889889e5fd29e42e2492ab2af4d7febae1922cb3513b740b21e97f12deb44b5927a3c3d'
         'SKIP'
         'e101c31ff9b68ec025183cbb199109d5bc94135d247c06fa903b97ccea6d3255b39b2780f3d1e3848ea68109ba91cdde5886d0a18d547b2f41d9643d2ac5bf5f'
+        'e41d07edb0d2098deda9bf5c5e3a9c3f34f858579b7aedb72a3488828e1def993c8557fa477eab6df59bb9c6175984e1bac1213d29cef710c5a46b3b3faff015'
         '02dd441cf6e4a7c2bc0de876f020b0784d811f77a5c6102dd075d67b07158dbc53c8b4d62bc8035283d4f349008574b1c3fac03f4519d56ffd809cb5bcfb7bea'
         'db58b7deb24cea16fb84f56680f0000683f72e11a95039969878e3819607aad5e65af9d9f50007e7710609065c0e3ebb9b30c1d929162b74eca5e74434d82cf1'
         'de31693cea5f452a9c8c0d1cf5210a6e67c0176f8b1a4d74106f2e803911569e9fdbb2301b3b5dc7ad6a6da285026b1a3ed3de52117d216b030cf0d92348909d')
@@ -67,7 +70,7 @@ _pick() {
 prepare() {
   # add distribution defaults to main.cf (alias_maps and alias_database)
   patch -Np1 -d $pkgbase-$pkgver -i ../$pkgbase-3.5.8-main_defaults.patch
-  sed -e s/btree:/lmdb:/ -i $pkgbase-$pkgver/src/global/mail_params.h
+  patch -Np1 -d $pkgbase-$pkgver -i ../$pkgbase-3.9.0-mail_params.patch
 }
 
 build() {

postfix-3.9.0-mail_params.patch

+--- a/src/global/mail_params.h	2024-02-20 16:37:05.000000000 +0100
++++ b/src/global/mail_params.h	2024-03-22 00:04:31.689504363 +0100
+@@ -2932,7 +2932,7 @@
+ extern char *var_verify_service;
+ 
+ #define VAR_VERIFY_MAP			"address_verify_map"
+-#define DEF_VERIFY_MAP			"btree:$data_directory/verify_cache"
++#define DEF_VERIFY_MAP			"lmdb:$data_directory/verify_cache"
+ extern char *var_verify_map;
+ 
+ #define VAR_VERIFY_POS_EXP		"address_verify_positive_expire_time"
+@@ -3748,7 +3748,7 @@
+   * postscreen(8)
+   */
+ #define VAR_PSC_CACHE_MAP	"postscreen_cache_map"
+-#define DEF_PSC_CACHE_MAP	"btree:$data_directory/postscreen_cache"
++#define DEF_PSC_CACHE_MAP	"lmdb:$data_directory/postscreen_cache"
+ extern char *var_psc_cache_map;
+ 
+ #define VAR_SMTPD_SERVICE	"smtpd_service_name"