Confirming that if I edit util.c and replace LINE_MAX with 65535 (since SMTPD_LINE_MAX is out of scope here) then I can successfully communicate with O365 mail servers. Not sure what nasty side-effects that edit could have, though – looking for input! -Adam
From: Adam Thompson Sent: Wednesday, September 30, 2026 3:50 AM To: '[email protected]' <[email protected]> Subject: mta error reason=Bad response: line too long when talking to O365 Hi, I’m having difficulty getting /usr/sbin/smtpd 7.9-STABLE to communicate successfully with O365, getting “Bad response: line too long” errors. I’m using a secrets file to authenticate to O365 in order to relay mail; the opensmtpd instance in question is my internal SMTP relay… or at least that’s the intention, I don’t see any need for any other MTAs in such a straightforward application. Looking at the output from a `-T all` invocation, and comparing that to smtp_client.c, I’m not sure I understand what the failing input is. I see from `-T all`, in part: […everything is fine up until this point, I’ve connected, STARTTLS’d, and authenticated…] mta: 0x28c3d5ef6d0: <<< 354 Start mail input; end with <CRLF>.<CRLF> mta: 0x28c3d5ef6d0: MTA_DATA -> MTA_BODY mta: 0x28c3d5ef6d0: >>> [...419 bytes...] mta: 0x28c3d5ef6d0: IO_LOWAT <io:0x28c79fd6f00 fd=14 to=300000 fl=W tls=TLSv1.3:TLS_AES_256_GCM_SHA384 ib=0 ob=0> mta: 0x28c3d5ef6d0: MTA_BODY -> MTA_BODY mta: 0x28c3d5ef6d0: end-of-file mta: 0x28c3d5ef6d0: MTA_BODY -> MTA_EOM mta: 0x28c3d5ef6d0: >>> . mta: 0x28c3d5ef6d0: IO_LOWAT <io:0x28c79fd6f00 fd=14 to=300000 fl=W tls=TLSv1.3:TLS_AES_256_GCM_SHA384 ib=0 ob=0> mta: 0x28c3d5ef6d0: IO_DATAIN <io:0x28c79fd6f00 fd=14 to=300000 fl=R tls=TLSv1.3:TLS_AES_256_GCM_SHA384 ib=4381 ob=0> mta: 0x28c3d5ef6d0: <<< 554 5.2.252 SendAsDenied; [email protected]<mailto:[email protected]> not allowed to send as [email protected]<mailto:[email protected]>; STOREDRV.Submission.Exception:SendAsDeniedException.MapiExceptionSendAsDenied; Failed to process message due to a permanent exception with message [BeginDiagnosticData]Cannot submit message. 1.84300:01000000, 1.84300:0B000000, 1.84300:0A000000, 1.84300:0A000000, 1.84300:0E000000, 1.84300:32000000, 1.73948:00000000, 5.71140:67000000446F526F70730000, 1.108572:00000000, 0.117068:76657200, 1.79180:0B000000, 1.79180:0A000000, 1.79180:0A000000, 1.79180:0E000000, 1.79180:32000000, 1.79180:FA000000 , 255.73100:6E743D41, 5.95292:67000000446F526F70730072, 8.111356:9552F9FE86593ECC1F1F572B2F8F6BAC1F1F572B, 0.38698:80DEE83A, 1.41134:86000000, 1.98628:00000000, 1.41134:86000000, 1.98628:00000000, 1.41134:86000000, 1.98628:00000000, 1.41134:46000000, 1.98628:00000000, 0.37692:0A000000, 0.37948:00000000, 5.33852:0 0000000534D545000000000, 7.36354:010000000000010900000000, 1.46439:0A000000, 1.115228:00000000, 0.104668:12000000, 1.44903:25000000, 1.115228:00000000, 12.56248:DC04000053656E64417320636865636B206661696C65642062656375617365204149206973206E756C6C0000, 7.40748:010000000000010B01000000, 7.57132:00000000000000000F010 480, 4.39640:DC040000, 1.63016:32000000, 8.45434:888C4079C982DB429564573D7EFC63AA38662D36, 0.104348:34393162, 5.46798:040000004D61696C4974656D5375626D697373696F6E00542031302E, 7.51330:6E32E3BDC31EDF088F000100, 5.10786:0000000031352E32312E303437322E3030353A595131505230314D4231313930323A64316565613638662D366634302D 343931622D616435352D3430623034373664643163313A383338303A2E4E45542031302E302E313100000000, 0.39570:00000000, 1.55954:0B000000, 0.40818:02000000, 1.33010:0B000000, 2.54258:00000000, 0.59634:02000000, 1.56562:00000000, 1.33010:0B000000, 2.54258:00000000, 0.59634:00000000, 1.56562:00000000, 1.55954:0A000000, 1.33010: 0A000000, 2.54258:00000000, 0.40002:03000000, 1.56562:00000000, 1.33010:0A000000, 2.54258:00000000, 0.40002:00000000, 1.56562:00000000, 1.55954:0A000000, 1.33010:0A000000, 2.54258:00000000, 0.40002:00000000, 1.56562:00000000, 1.33010:0A000000, 2.54258:00000000, 0.40002:01000000, 1.56562:00000000, 1.64146:0E000000 , 1.33010:0E000000, 2.54258:00000000, 1.33010:0E000000, 2.54258:00000000, 1.64146:32000000, 1.33010:32000000, 2.54258:DC040000, 1.33010:32000000, 2.54258:DC040000, 255.79500:00000000, 0.100684:00000000, 255.66700:00000000, 5.95292:67000000446F526F70730072, 8.111356:9552F9FE86593ECC1F1F572B2F8F6BAC1F1F572B, 0.3869 8:80DEE83A, 1.41134:86000000, 1.98628:00000000, 1.41134:86000000, 1.98628:00000000, 1.41134:86000000, 1.98628:00000000, 1.41134:46000000, 1.98628:00000000, 0.37692:0A000000, 0.37948:00000000, 5.33852:00000000534D545000000000, 7.36354:010000000000010900000000, 1.46439:0A000000, 1.115228:00000000, 0.104668:12000000 , 1.44903:25000000, 1.115228:00000000, 12.56248:DC04000053656E64417320636865636B206661696C65642062656375617365204149206973206E756C6C0000, 7.40748:010000000000010B01000000, 7.57132:00000000000000000F010480, 4.39640:DC040000, 1.63016:32000000, 8.45434:888C4079C982DB429564573D7EFC63AA38662D36, 0.104348:34393162, 5.4 6798:040000004D61696C4974656D5375626D697373696F6E00542031302E, 7.51330:6E32E3BDC31EDF088F000100, 5.10786:0000000031352E32312E303437322E3030353A595131505230314D4231313930323A64316565613638662D366634302D343931622D616435352D3430623034373664643163313A383338303A2E4E45542031302E302E313100000000, 0.39570:00000000, 1.559 54:0B000000, 0.40818:02000000, 1.33010:0B000000, 2.54258:00000000, 0.59634:02000000, 1.56562:00000000, 1.33010:0B000000, 2.54258:00000000, 0.59634:00000000, 1.56562:00000000, 1.55954:0A000000, 1.33010:0A000000, 2.54258:00000000, 0.40002:03000000, 1.56562:00000000, 1.33010:0A000000, 2.54258:00000000, 0.40002:00000 000, 1.56562:00000000, 1.55954:0A000000, 1.33010:0A000000, 2.54258:00000000, 0.40002:00000000, 1.56562:00000000, 1.33010:0A000000, 2.54258:00000000, 0.40002:01000000, 1.56562:00000000, 1.64146:0E000000, 1.33010:0E000000, 2.54258:00000000, 1.33010:0E000000, 2.54258:00000000, 1.64146:32000000, 1.33010:32000000, 2.5 4258:DC040000, 1.33010:32000000, 2.54258:DC040000, 255.97900:00000000, 4.120460:DC040000, 1.52466:02000000, 1.52466:02000000, 1.42738:09000000, 0.37698:08000000, 1.42738:09000000, 0.37698:01000000, 1.52466:01000000, 0.60402:33000000, 1.52466:01000000[EndDiagnosticData] [Hostname=YQ1PR01MB11902.CANPRD01.PROD.OUTLO OK.COM] 2f15c431563c0591 mta error reason=Bad response: line too long 2f15c431563c0591 mta delivery evpid=ff8be9c9796c8290 from=<[email protected]<mailto:[email protected]>> to=<[email protected]<mailto:[email protected]>> rcpt=<-> source="172.31.31.196" relay="52.96.157.114 (52.96.157.114)" delay=3m24s result="TempFail" stat="Bad response: line too long" mproc: dispatcher -> control : 46 IMSG_STAT_DECREMENT mproc: dispatcher -> control : 50 IMSG_STAT_DECREMENT mproc: dispatcher -> control : 42 IMSG_STAT_DECREMENT debug: mta: 0x28c3d5ef6d0: session done mproc: dispatcher -> control : 45 IMSG_STAT_DECREMENT debug: mta_route_collect([] <-> 52.96.157.114 (52.96.157.114)) debug: mta: connecting with [connector:[]->[relay:smtp.office365.com,port=25,smtp+tls,auth=secrets:o365_creds,mx],0x0] debug: mta: no task for connector debug: mta: mta_route_unref(): keeping route [] <-> 52.96.157.114 (52.96.157.114) alive for 3s (imposed delay) mproc: dispatcher -> queue : 41 IMSG_MTA_DELIVERY_TEMPFAIL debug: mta: flush for ff8be9c9796c8290 (-> [email protected]<mailto:[email protected]>) The error “Bad response: line too long” doesn’t appear in its entirety, so I’m grepping for partial hits. My first thought was that insanely-long 554 error from O365 was tripping up smtpd, but looking at the code very early in smtp_client.c : smtp_client_readline, it looks like the “line too long” error is either being triggered by the *next* line, which is not logged anywhere, or by code elsewhere… but in any case params.linemax is set to 16k which surely would be enough for anything in use today? My second thought is that the error is coming from util.c : parse_smtp_response, which is (perhaps erroneously?) comparing against LINE_MAX (i.e. 2048), instead of SMTP_LINE_MAX. Ultimately, there are enough moving parts in the code base that I’m not really sure where it’s coming from. It’s been forever since I last had to recompile bits of an OpenBSD system, but I’m pretty sure I remember how to if needed. Any ideas? -Adam Thompson [email protected]<mailto:[email protected]>
