up to 4 connections

src/imap/client.rs

@@ -206,11 +206,14 @@ impl Client {
                 connection_attempt_set.spawn(fut);
             }
 
-            // Start second connection attempt 300 ms after the first.
-            delay_set.spawn(tokio::time::sleep(Duration::from_millis(300)));
-
-            // Start third connection attempt if we have not managed to connect in 10 seconds.
-            delay_set.spawn(tokio::time::sleep(Duration::from_secs(10)));
+            // Start second, third and fourth connection attempt 300 ms, 10 s and 15 s after the first.
+            for delay in [
+                Duration::from_millis(300),
+                Duration::from_secs(10),
+                Duration::from_secs(15),
+            ] {
+                delay_set.spawn(tokio::time::sleep(delay));
+            }
 
             let mut first_error = None;
             loop {

src/smtp/connect.rs

@@ -177,11 +177,14 @@ async fn connect_stream(
             connection_attempt_set.spawn(fut);
         }
 
-        // Start second connection attempt 300 ms after the first.
-        delay_set.spawn(tokio::time::sleep(Duration::from_millis(300)));
-
-        // Start third connection attempt if we have not managed to connect in 10 seconds.
-        delay_set.spawn(tokio::time::sleep(Duration::from_secs(10)));
+        // Start second, third and fourth connection attempt 300 ms, 10 s and 15 s after the first.
+        for delay in [
+            Duration::from_millis(300),
+            Duration::from_secs(10),
+            Duration::from_secs(15),
+        ] {
+            delay_set.spawn(tokio::time::sleep(delay));
+        }
 
         let mut first_error = None;
         loop {