Exception on POP3 GetMessageHeadersAsync with Gmail

[felixcollins]

Hi, I'm not that familiar with email protocols so forgive me if I've missed something obvious.

I'm calling GetMessageHeadersAsync (MailKit 1.0.0) and I get this stack trace.

10-23 14:54:34.226 E/        (19207): MailKit.Net.Pop3.Pop3ProtocolException: Unexpected response from server: MIME-Version: 1.0
10-23 14:54:34.226 E/        (19207):   at MailKit.Net.Pop3.Pop3Engine.ReadResponse (MailKit.Net.Pop3.Pop3Command pc) [0x00000] in <filename unknown>:0 
10-23 14:54:34.226 E/        (19207):   at MailKit.Net.Pop3.Pop3Engine.Iterate () [0x00000] in <filename unknown>:0 
10-23 14:54:34.226 E/        (19207):   at MailKit.Net.Pop3.Pop3Client.GetMessagesForSequenceIds (IList`1 seqids, Boolean headersOnly, CancellationToken cancellationToken) [0x00000] in <filename unknown>:0 
10-23 14:54:34.226 E/        (19207):   at MailKit.Net.Pop3.Pop3Client.GetMessageHeaders (IList`1 indexes, CancellationToken cancellationToken) [0x00000] in <filename unknown>:0 
10-23 14:54:34.226 E/        (19207):   at MailKit.MailSpool+<>c__DisplayClass30.<GetMessageHeadersAsync>b__2f () [0x00000] in <filename unknown>:0 

The relevant code snippet

await client.ConnectAsync(request.EmailServerAddress, (int)request.EmailPort, request.EmailUseSSL, ct);

// Note: since we don't have an OAuth2 token, disable
// the XOAUTH2 authentication mechanism.
client.AuthenticationMechanisms.Remove("XOAUTH2");

await client.AuthenticateAsync(request.EmailUserName, request.EmailUserPassword, ct);

var count = await client.GetMessageCountAsync(ct);

var allHeaderLists = await client.GetMessageHeadersAsync(Enumerable.Range(0, count - 1).ToList(), ct);

I did have it working with an older version of MailKit using GetMessageHeaderAsync (singular).

Any ideas?

[jstedfast]

I'm probably going to need the protocol logs to diagnose this problem. Could you pass a ProtocolLogger to the Pop3Client .ctor?

[felixcollins]

Connected to pops://pop.gmail.com:995/
S: +OK Gpop ready for requests from 203.86.205.98 kk16mb4935504icc
C: CAPA
S: +OK Capability list follows
S: USER
S: RESP-CODES
S: EXPIRE 0
S: LOGIN-DELAY 300
S: TOP
S: UIDL
S: X-GOOGLE-RICO
S: SASL PLAIN XOAUTH2
S: .
C: AUTH PLAIN
S: + 
C: AGxhb3V0cnlAZ21haWwuY29tAHdlYWtwYXNzd29yZA==
S: +OK Welcome.
C: CAPA
S: +OK Capability list follows
S: USER
S: RESP-CODES
S: PIPELINING
S: EXPIRE 0
S: LOGIN-DELAY 300
S: TOP
S: UIDL
S: X-GOOGLE-RICO
S: .
C: STAT
S: +OK 20 20718932
C: TOP 1 0
C: TOP 2 0
C: TOP 3 0
C: TOP 4 0
C: TOP 5 0
C: TOP 6 0
C: TOP 7 0
C: TOP 8 0
C: TOP 9 0
C: TOP 10 0
C: TOP 11 0
C: TOP 12 0
C: TOP 13 0
C: TOP 14 0
C: TOP 15 0
C: TOP 16 0
C: TOP 17 0
C: TOP 18 0
C: TOP 19 0
S: +OK message follows
S: MIME-Version: 1.0
S: x-no-auto-attachment: 1
S: Received: by 10.96.40.106; Tue, 8 Jul 2014 21:01:32 -0700 (PDT)
S: Date: Tue, 8 Jul 2014 21:01:32 -0700
S: Message-ID: <CAHwOFDw6gpW8_KW8R7cg5yNbv4E7O_j+jrCBcoVViSMjHiC6PQ@mail.gmail.com>
S: Subject: Three tips to get the most out of Gmail
S: From: Gmail Team <mail-noreply@google.com>
S: To: KG Test <laoutry@gmail.com>
S: Content-Type: multipart/alternative; boundary=20cf3074af8482c58404fdbac36b
S: 
S: .
S: +OK message follows
S: MIME-Version: 1.0
S: x-no-auto-attachment: 1
S: Received: by 10.96.40.106; Tue, 8 Jul 2014 21:01:33 -0700 (PDT)
S: Date: Tue, 8 Jul 2014 21:01:33 -0700
S: Message-ID: <CAHwOFDzTEMBrhg4T2CyhKRxNNn+9Tck8e-Qx0U23vw3ogwHsFQ@mail.gmail.com>
S: Subject: The best of Gmail, wherever you are
S: From: Gmail Team <mail-noreply@google.com>
S: To: KG Test <laoutry@gmail.com>
S: Content-Type: multipart/alternative; boundary=20cf3074d72c8812c804fdbac3c6
S: 
S: .

[jstedfast]

Thanks, this should help. Also I didn't realize GMail supports PIPELINING...

The problem, I imagine, has something to do with a bug in MailKit's PIPELINING support.

[jstedfast]

Okay, that commit should fix things... I will warn you, though, that I have not actually tested it yet.

If you could get back to me as to whether it works for you, that would be great.

[jstedfast]

I've confirmed the fix now with my gmail test account.

[felixcollins]

Wow fast! Thanks for that. Sorry I didn't get back to you, I was dragged off to other things.

[jstedfast]

I pushed MailKit v1.0.1 this morning to NuGet if you are using that.

[felixcollins]

1.0.1 via NuGet works for me. Thanks again...

[jstedfast]

no prob, glad it works :-)