通过 SMTP 发送电子邮件到 gmail 帐户

Question

我正在尝试制作一个 SMTP 客户端库，并尝试先通过命令行发送电子邮件。

250 SMTPUTF8
EHLO gmail.com
write to 0x7fb0e6c16130 [0x7fb0ea011a03] (37 bytes => 37 (0x25))
0000 - 17 03 03 00 20 3f a5 65-6f 8a a3 b8 a7 13 7e 70   .... ?.eo.....~p
0010 - 57 a1 7b ca c1 4b 25 56-39 b5 df d6 c4 b7 49 c1   W.{..K%V9.....I.
0020 - 32 f2 f4 5a c5                                    2..Z.
read from 0x7fb0e6c16130 [0x7fb0ea00d803] (5 bytes => 5 (0x5))
0000 - 17 03 03 00 c2                                    .....
read from 0x7fb0e6c16130 [0x7fb0ea00d808] (194 bytes => 194 (0xC2))
0000 - 23 b5 8f 8e 31 26 8a dd-98 ce fd 73 58 8b e4 f5   #...1&.....sX...
0010 - 0a d6 8d 7b a8 a0 97 fb-ef 48 84 9b 10 f4 58 2b   ...{.....H....X+
0020 - 65 0c 61 29 17 f7 41 0b-c4 59 8a 87 87 4b f7 b9   e.a)..A..Y...K..
0030 - 7a 68 8c f8 1b ec 05 bb-fa 97 dc 81 76 ba 12 86   zh..........v...
0040 - ed a6 6f 06 44 74 e1 80-4c 24 37 a4 06 a6 40 9d   ..o.Dt..L...@.
0050 - c9 57 b2 2d 6c a7 fe cf-bb 7b 32 4e 01 f2 65 94   .W.-l....{2N..e.
0060 - b5 1f f9 aa eb 73 c6 b8-6c 93 71 89 2c 84 83 ad   .....s..l.q.,...
0070 - 73 bb 5a 8b 63 c4 5a 94-d9 65 fa 2e 3b 1a 3d 21   s.Z.c.Z..e..;.=!
0080 - f8 6f 97 f0 61 1d 13 b3-ee 68 cf ed 92 aa dd e0   .o..a....h......
0090 - 86 16 e3 14 71 ef b0 28-74 ec fa ba ad 9f e2 6d   ....q..(t......m
00a0 - 05 c1 39 7a 65 71 21 34-e8 a7 be d1 6c 39 68 42   ..9zeq!4....l9hB
00b0 - 84 a2 8d 9e 7c 03 57 49-6f 5b c1 af 78 2d 72 e5   ....|.WIo[..x-r.
00c0 - 47 67                                             Gg
250-mx.google.com at your service, [2800:e2:37f:ecc6:9426:2eed:fdd4:795b]
250-SIZE 157286400
250-8BITMIME
250-ENHANCEDSTATUSCODES
250-PIPELINING
250-CHUNKING
250 SMTPUTF8
MAIL FROM:kyle@live.com
write to 0x7fb0e6c16130 [0x7fb0ea011a03] (46 bytes => 46 (0x2E))
0000 - 17 03 03 00 29 1a 31 f6-c0 39 da 57 95 3e 85 0c   ....).1..9.W.>..
0010 - 48 86 29 1c a5 c2 80 cb-40 79 ef fa 66 dd e7 10   H.).....@y..f...
0020 - 8e dd 14 d2 f3 c8 07 98-ff 06 68 8b 4d b2         ..........h.M.
read from 0x7fb0e6c16130 [0x7fb0ea00d803] (5 bytes => 5 (0x5))
0000 - 17 03 03 00 44                                    ....D
read from 0x7fb0e6c16130 [0x7fb0ea00d808] (68 bytes => 68 (0x44))
0000 - 4a 7d f0 e2 01 00 00 eb-8b c0 82 70 fd 09 1a 50   J}.........p...P
0010 - 3b b3 fb ab 8a a1 83 df-af cd c8 bb 96 4f eb 19   ;............O..
0020 - 38 19 fa 4c 28 5d 75 f9-a4 d5 20 38 c4 f3 b6 db   8..L(]u... 8....
0030 - cd 44 3f 36 6a 8c f6 79-38 2e d3 2f b2 c4 4d 91   .D?6j..y8../..M.
0040 - 51 e8 2f ff                                       Q./.
555 5.5.2 Syntax error. d7si1665405vsj.297 - gsmtp

问题是无论我使用什么电子邮件地址都会出现语法错误。我做错了什么？

Answer 1

源邮箱中缺少方括号。

The first step in the procedure is the MAIL command.
  MAIL FROM:<reverse-path> [SP <mail-parameters> ] <CRLF>
The portion of the first or only argument contains the source mailbox (between "<" and ">" brackets), which can be used to report errors (see Section 4.2 for a discussion of error reporting). If accepted, the SMTP server returns a "250 OK" reply.

-- from RFC 5321 Section 3.3 (emphasis mine)

改变这个

MAIL FROM:kyle@live.com

进入这个：

MAIL FROM:<kyle@live.com>

话虽如此..

I'm trying to make a SMTP client library

请不要那样做！几乎每种编程语言都已经有这样的库，最常见的甚至在各自的标准库中。这些作者通常比你我更仔细地考虑了更多的边缘案例。不要重新发明轮子，尤其是在处理邮件时（很容易导致互操作性问题或 spam/abuse 的新向量）。

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