diff --git a/Package.resolved b/Package.resolved
index 0469230..30daeca 100644
--- a/Package.resolved
+++ b/Package.resolved
@@ -1,5 +1,5 @@
 {
-  "originHash" : "4df95539bc96e03b7eee2a67456b2458dc5f67169bc92ba36d567dd1f77f5e6a",
+  "originHash" : "3d9b0f6ee85503e2da9b81ef8424af582ca2ee33dc76faf6d5c52e9c6586532b",
   "pins" : [
     {
       "identity" : "jsonfoundation",
@@ -177,8 +177,7 @@
       "kind" : "remoteSourceControl",
       "location" : "https://github.com/apple/swift-nio-imap",
       "state" : {
-        "revision" : "d67f1243f731457cb9f2eb0beb27eff9e533bf7b",
-        "version" : "0.4.0"
+        "revision" : "14ad3887dab9ca5aba38ee0ace18fddf40e9491f"
       }
     },
     {
@@ -199,15 +198,6 @@
         "version" : "1.1.1"
       }
     },
-    {
-      "identity" : "swift-se0270-range-set",
-      "kind" : "remoteSourceControl",
-      "location" : "https://github.com/apple/swift-se0270-range-set.git",
-      "state" : {
-        "revision" : "7d6d7531d40e95f4e1e26f6565265be6df228911",
-        "version" : "1.0.1"
-      }
-    },
     {
       "identity" : "swift-service-lifecycle",
       "kind" : "remoteSourceControl",
@@ -258,8 +248,7 @@
       "kind" : "remoteSourceControl",
       "location" : "https://github.com/Cocoanetics/SwiftMail",
       "state" : {
-        "revision" : "1a681959579add669ae785d3d080b169156df60a",
-        "version" : "1.15.0"
+        "revision" : "c3b7bc3a6b77509655668651c744934470fa2d86"
       }
     },
     {
@@ -276,8 +265,8 @@
       "kind" : "remoteSourceControl",
       "location" : "https://github.com/Cocoanetics/SwiftText",
       "state" : {
-        "revision" : "f9279a17cbb139defb5d88ca15685cf3bd0a672a",
-        "version" : "2.3.0"
+        "revision" : "15e176a1910ece26c87468e151714f6253a6b385",
+        "version" : "2.4.0"
       }
     },
     {
diff --git a/Package.swift b/Package.swift
index 69aceac..39ed1a5 100644
--- a/Package.swift
+++ b/Package.swift
@@ -4,7 +4,8 @@ import PackageDescription
 let package = Package(
     name: "Post",
     platforms: [
-        .macOS("14.0")
+        // SwiftMail's pinned swift-nio-imap declares macOS 15 (see below).
+        .macOS("15.0")
     ],
     products: [
         .library(
@@ -57,7 +58,15 @@ let package = Package(
         // 1.15.0 adds searchCount, which countMessages uses: it asks for COUNT, MIN
         // and MAX without the UID list, whose reply line for a large mailbox
         // exceeds swift-nio-imap's 8 KiB line limit.
-        .package(url: "https://github.com/Cocoanetics/SwiftMail", .upToNextMajor(from: "1.15.0")),
+        // Pinned by revision to SwiftMail 1.16.0 (#253), which removes that 8 KiB
+        // limit: it pins swift-nio-imap to main for apple/swift-nio-imap#849 and
+        // hands IMAPClientHandler its 1 MB responseBufferLimit. Before it, the
+        // BODYSTRUCTURE of a mail with 74 attachments was one reply line too long,
+        // so every list, search and fetch that touched the mail failed with
+        // PayloadTooLargeError. A revision-pinned dependency can't be resolved by
+        // version, so return to .upToNextMajor once swift-nio-imap tags a release
+        // with #849 and SwiftMail moves back to a version requirement.
+        .package(url: "https://github.com/Cocoanetics/SwiftMail", revision: "c3b7bc3a6b77509655668651c744934470fa2d86"),
         // 2.2.0 replaced the revision-pinned ZIPFoundation with tagged
         // swift-archive, so SwiftText is a normal version requirement again.
         // It declares swift-tools-version 6.3, which sets Post's toolchain
diff --git a/README.md b/README.md
index 44822bc..0f10c6d 100644
--- a/README.md
+++ b/README.md
@@ -93,7 +93,7 @@ Combine IDLE with handler scripts to build a "mail room" that automatically sort
 ## Getting Started
 
 ### Requirements
-- macOS 14.0+
+- macOS 15.0+
 - Swift 6.3+ (Xcode 26.4+)
 
 ### Build & Run