(CaseClauseError) no case clause matching: <<0>>

[puruzio]

I am getting the same error mentioned in https://github.com/gen-smtp/gen_smtp/issues/94, but in a different situation. Debugging with io:format("~p~n", [Packet])` in gen_smtp_client.erl displays the following where the 4th item is <<21.3.3.0.2.2.10>>. I'm not sure what that represents.

01:12:05.546 [info] Sent 200 in 13ms

<<"220 Xeams SMTP server;  - Xeams SMTP server; Version: 8.8 - build: 6281; 11/5/23 3:12 AM\r\n">>
<<"250-10.34.72.4. Pleased to meet you\r\n">>
<<"220 Go ahead \r\n">>
<<21,3,3,0,2,2,10>>

FYI. The same program run on another machine doesn't generate this error, and it prints the following output. It appears to me that the network environment or cert authority setting of the first machine is somehow different from this other machine, leading to different outcomes.

<<"220 Xeams SMTP server;  - Xeams SMTP server; Version: 8.8 - build: 6281; 11/5/23 3:14 AM\r\n">>
<<"250-10.34.72.4. Pleased to meet you\r\n">>
<<"220 Go ahead \r\n">>

01:14:36.034 [warning] Description: 'Authenticity is not established by certificate path validation'
     Reason: 'Option {verify, verify_peer} and cacertfile/cacerts is missing'

<<"250-10.34.72.4. Pleased to meet you\r\n">>
<<"250 OK\r\n">>
<<"250 OK\r\n">>
<<"250 OK\r\n">>
<<"354 Start mail input; end with <CRLF>.<CRLF>\r\n">>
<<"250 2.6.0 Queued mail for delivery\r\n">>

Below is the full error message.

01:12:05.563 [error] Task #PID<0.1038.0> started from #PID<0.1030.0> terminating

** (CaseClauseError) no case clause matching: <<0>>
    (gen_smtp 1.2.0) e:/Data/elixir-stuff/fin_reporting_phx16/deps/gen_smtp/src/gen_smtp_client.erl:842: :gen_smtp_client.read_possible_multiline_reply/1
    (gen_smtp 1.2.0) e:/Data/elixir-stuff/fin_reporting_phx16/deps/gen_smtp/src/gen_smtp_client.erl:416: :gen_smtp_client.try_MAIL_FROM/4
    (gen_smtp 1.2.0) e:/Data/elixir-stuff/fin_reporting_phx16/deps/gen_smtp/src/gen_smtp_client.erl:400: :gen_smtp_client.try_sending_it/4
    (gen_smtp 1.2.0) e:/Data/elixir-stuff/fin_reporting_phx16/deps/gen_smtp/src/gen_smtp_client.erl:300: :gen_smtp_client.send_it/2
    (bamboo_smtp 4.2.2) lib/bamboo/adapters/smtp_adapter.ex:87: Bamboo.SMTPAdapter.deliver/2
    (bamboo 2.2.0) lib/bamboo/strategies/task_supervisor_strategy.ex:24: anonymous fn/3 in Bamboo.TaskSupervisorStrategy.deliver_later/3
    (elixir 1.15.5) lib/task/supervised.ex:101: Task.Supervised.invoke_mfa/2

Function: #Function<0.95237244/0 in Bamboo.TaskSupervisorStrategy.deliver_later/3>

    Args: []

[Vagabond]

I don't see how this badmatch happens, given read_possible_multiline_reply should not be able to return just an untagged binary.

[Vagabond]

ascii code 21 is "negative acknowledge", but I didn't think SMTP used ascii control characters. I think the server doesn't like your TLS handshake, or whatever.

[Vagabond]

Can you try supplying trace_fun to the client options: https://github.com/gen-smtp/gen_smtp/blob/1.2.0/src/gen_smtp_client.erl#L946C30-L946C39

[Vagabond]

I suspect the TLS negotiaton goes wrong here https://github.com/gen-smtp/gen_smtp/blob/1.2.0/src/gen_smtp_client.erl#L777, and the server thinks we're doing TLS and the client doesn't

[puruzio]

Changing to tls: :never fixed the issue. Thank you!

[Vagabond]

It might be helpful if you could capture more information so we could fix the issue properly.

[puruzio]

What's the suggested steps I should follow to do so?

[Vagabond]

You could privately let me try using the server, or you could pass [{trace_fun, fun io:format/2}] to the client options and see what the trace gives you, or add a io:format around https://github.com/gen-smtp/gen_smtp/blob/1.2.0/src/gen_smtp_client.erl#L777

[puruzio]

Else -> io:format("~p~n", [trace(Options, "~p~n", [Else])]), false

printed "ok"

Let me know if that's not what you meant.

[Vagabond]

Weird, that means that ssl:connect() is returning ok, not {ok, Socket}. What OTP version is this?

[puruzio]

OTP 26