fix: repaired smtp configuration for port 587

config/runtime.exs

@@ -263,20 +263,25 @@ if config_env() == :prod do
 
     verify_mode = if smtp_verify_peer, do: :verify_peer, else: :verify_none
 
+    base_smtp_opts = [
+      adapter: Swoosh.Adapters.SMTP,
+      relay: String.trim(smtp_host_env),
+      port: smtp_port_env,
+      username: System.get_env("SMTP_USERNAME"),
+      password: smtp_password_env,
+      ssl: smtp_ssl_mode == "ssl",
+      tls: if(smtp_ssl_mode == "tls", do: :always, else: :never),
+      auth: :always,
+      tls_options: [verify: verify_mode]
+    ]
+
+    # Port 465: pass verify in sockopts for initial ssl:connect. Port 587: do not (gen_tcp rejects it).
     smtp_opts =
-      [
-        adapter: Swoosh.Adapters.SMTP,
-        relay: String.trim(smtp_host_env),
-        port: smtp_port_env,
-        username: System.get_env("SMTP_USERNAME"),
-        password: smtp_password_env,
-        ssl: smtp_ssl_mode == "ssl",
-        tls: if(smtp_ssl_mode == "tls", do: :always, else: :never),
-        auth: :always,
-        # tls_options: STARTTLS (587); sockopts: direct SSL (465).
-        tls_options: [verify: verify_mode],
-        sockopts: [verify: verify_mode]
-      ]
+      if smtp_ssl_mode == "ssl" do
+        Keyword.put(base_smtp_opts, :sockopts, verify: verify_mode)
+      else
+        base_smtp_opts
+      end
       |> Enum.reject(fn {_k, v} -> is_nil(v) end)
 
     config :mv, Mv.Mailer, smtp_opts