diff --git a/http_server.go b/http_server.go
index c17844e..f4a4411 100644
--- a/http_server.go
+++ b/http_server.go
@@ -13,6 +13,7 @@ import (
 
 	"github.com/pkg/errors"
 	"github.com/programmfabrik/apitest/internal/httpproxy"
+	"github.com/programmfabrik/apitest/pkg/lib/util"
 	"github.com/programmfabrik/golib"
 	"github.com/sirupsen/logrus"
 )
@@ -78,6 +79,8 @@ func (ats *Suite) StartHttpServer() {
 		run()
 	} else {
 		go run()
+
+		util.WaitForTCP(ats.HttpServer.Addr)
 	}
 }
 
diff --git a/pkg/lib/util/net.go b/pkg/lib/util/net.go
new file mode 100644
index 0000000..845b05c
--- /dev/null
+++ b/pkg/lib/util/net.go
@@ -0,0 +1,23 @@
+package util
+
+import (
+	"net"
+	"time"
+
+	"github.com/sirupsen/logrus"
+)
+
+// WaitForTCP polls indefinitely until it can connect to the given TCP address.
+func WaitForTCP(addr string) {
+	logrus.Infof("Waiting for TCP address %q to become connectable...", addr)
+
+	for {
+		c, err := net.Dial("tcp", addr)
+		if err == nil {
+			c.Close()
+			break
+		}
+
+		time.Sleep(10 * time.Millisecond)
+	}
+}
diff --git a/smtp_server.go b/smtp_server.go
index 53ba793..bfb36aa 100644
--- a/smtp_server.go
+++ b/smtp_server.go
@@ -8,6 +8,7 @@ import (
 	"github.com/sirupsen/logrus"
 
 	"github.com/programmfabrik/apitest/internal/smtp"
+	"github.com/programmfabrik/apitest/pkg/lib/util"
 )
 
 // StartSmtpServer starts the testing SMTP server, if configured.
@@ -29,6 +30,8 @@ func (ats *Suite) StartSmtpServer() {
 			logrus.Fatal("SMTP server ListenAndServe:", err)
 		}
 	}()
+
+	util.WaitForTCP(ats.SmtpServer.Addr)
 }
 
 // StopSmtpServer stops the SMTP server that was started using StartSMTPServer.