Running nixpkgs-update (https://nix-community.org/update-bot/) with UPDATE_INFO: fastmail-desktop 0 -> 1
attrpath: fastmail-desktop
Checking auto update branch...
[version] 
[version] skipping because derivation has updateScript
[rustCrateVersion] 
[rustCrateVersion] No cargoHash found
[golangModuleVersion] 
[golangModuleVersion] Not a buildGoModule package with vendorHash
[npmDepsVersion] 
[npmDepsVersion] No npmDepsHash
[updateScript] 
[updateScript] Success
[updateScript] this derivation will be built:
  /nix/store/zcif3lpffnn7mri92ihjanmgdk3sfn8k-packages.json.drv
building '/nix/store/zcif3lpffnn7mri92ihjanmgdk3sfn8k-packages.json.drv'...

Going to be running update for following packages:
 - fastmail-desktop-1.4.0

Press Enter key to continue...
Running update for:
Enqueuing group of 1 packages
 - fastmail-desktop-1.4.0: UPDATING ...
 - fastmail-desktop-1.4.0: DONE.

Packages updated!

Diff after rewrites:
diff --git a/pkgs/by-name/fa/fastmail-desktop/sources.nix b/pkgs/by-name/fa/fastmail-desktop/sources.nix
index 380636526ff8..5f16d348f379 100644
--- a/pkgs/by-name/fa/fastmail-desktop/sources.nix
+++ b/pkgs/by-name/fa/fastmail-desktop/sources.nix
@@ -1,26 +1,26 @@
 # Generated by ./update.sh - do not update manually!
-# Last updated: 2026-07-11
+# Last updated: 2026-07-29
 { fetchurl, fetchzip }:
 {
   aarch64-darwin = {
-    version = "1.4.0";
+    version = "1.5.1";
     src = fetchurl {
-      url = "https://dl.fastmailcdn.com/desktop/production/mac/arm64/Fastmail-1.4.0-arm64-mac.zip";
-      hash = "sha512-QyZZu6pwFJ0SkVye0/OtvNTligl6qKsYbpJfdPeHojPj+OqVyV8bavz15Lest+v7ALJhACZ3x+2kBiWa0ZCSow==";
+      url = "https://dl.fastmailcdn.com/desktop/production/mac/arm64/Fastmail-1.5.1-arm64-mac.zip";
+      hash = "sha512-z1RHyAatg5a7zAwgqaBZAmDN+rKgqyoFTO78EEIaeBKNHFje86duBi3H6SbAzF7wjL3Q1yHG/yvXtB3V1oQSww==";
     };
   };
   aarch64-linux = {
-    version = "1.4.0";
+    version = "1.5.1";
     src = fetchurl {
-      url = "https://dl.fastmailcdn.com/desktop/production/linux/arm64/com.fastmail.Fastmail-1.4.0-arm64.AppImage";
-      hash = "sha512-sw55AwedyijKTXWAAAaSi6sgGMGK0uF4nPtQRacp9VG5EwlC+0wedyO4ax2cWxhsVUSXnk9ngN4mkraSd07vag==";
+      url = "https://dl.fastmailcdn.com/desktop/production/linux/arm64/com.fastmail.Fastmail-1.5.1-arm64.AppImage";
+      hash = "sha512-IXJSHLK2toQ7ngnfpo37BzMtk5RSJ2z4vZWCfC1jnMh9SjetxpuJMoGt/p9eDeMWJWLehpQAvBNmEwLVRT7rCA==";
     };
   };
   x86_64-linux = {
-    version = "1.4.0";
+    version = "1.5.1";
     src = fetchurl {
-      url = "https://dl.fastmailcdn.com/desktop/production/linux/x64/com.fastmail.Fastmail-1.4.0.AppImage";
-      hash = "sha512-0hNTRFNAnnLPq19isnaoVlXNl6za4Z5o6yh9ovU564JBMyAjsDNHk8h+2zArSSpydaUky6tIgAUsOhhWrIRtcg==";
+      url = "https://dl.fastmailcdn.com/desktop/production/linux/x64/com.fastmail.Fastmail-1.5.1.AppImage";
+      hash = "sha512-8ULXlSCeT/MlO0qmcwKHgmaSiZvz7dAWGLiWqoOorSkWsNZ+9dRu2PhZmBkdU3k0R2cWJsA6xA4UViZtOScP0Q==";
     };
   };
 }

No auto update branch exists
There might already be an open PR for this update:
- fastmail-desktop: 1.4.0 -> 1.5.1
  URL "https://api.github.com/repos/NixOS/nixpkgs/issues/544808"