diff --git a/connpool.go b/connpool.go
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--- /dev/null
+++ b/connpool.go
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+// SPDX-FileCopyrightText: 2022-2024 The go-mail Authors
+//
+// SPDX-License-Identifier: MIT
+
+package mail
+
+import "net"
+
+// Parts of the connection pool code is forked from https://github.com/fatih/pool/
+// Thanks to Fatih Arslan and the project contributors for providing this great
+// concurrency template.
+
+// Pool interface describes a connection pool implementation. A Pool is
+// thread-/go-routine safe.
+type Pool interface {
+	// Get returns a new connection from the pool. Closing the connections returns
+	// it back into the Pool. Closing a connection when the Pool is destroyed or
+	// full will be counted as an error.
+	Get() (net.Conn, error)
+
+	// Close closes the pool and all its connections. After Close() the pool is
+	// no longer usable.
+	Close()
+
+	// Len returns the current number of connections of the pool.
+	Len() int
+}