diff --git a/changelog.d/6026.feature b/changelog.d/6026.feature
new file mode 100644
index 000000000..2489ff09b
--- /dev/null
+++ b/changelog.d/6026.feature
@@ -0,0 +1 @@
+Stop sending federation transactions to servers which have been down for a long time.
diff --git a/synapse/util/retryutils.py b/synapse/util/retryutils.py
index 33263fe20..b740913b5 100644
--- a/synapse/util/retryutils.py
+++ b/synapse/util/retryutils.py
@@ -28,8 +28,8 @@ MIN_RETRY_INTERVAL = 10 * 60 * 1000
 # how much we multiply the backoff by after each subsequent fail
 RETRY_MULTIPLIER = 5
 
-# a cap on the backoff
-MAX_RETRY_INTERVAL = 24 * 60 * 60 * 1000
+# a cap on the backoff. (Essentially none)
+MAX_RETRY_INTERVAL = 2 ** 63
 
 
 class NotRetryingDestination(Exception):