Can't connect to Comcast/Xfinity SMTP server
I can't send mail via smtp.comcast.net. I can connect to IMAP and get mail, and I can send from my iphone and (new) Outlook. Running TB v142.0 (64 bit) on Windows 11. Issue is reproducible on second system. When I try to send mail, client tries for 1 minute, then times out with "Sending of the message failed. The message could not be sent because the connection to Outgoing server (SMTP) smtp.comcast.net timed out. Try again."
TB log says: 14:17:11.775 1756750631775 addons.xpi WARN Checking C:\Program Files\Mozilla Thunderbird\distribution\extensions for addons 14:19:37.714 mailnews.smtp: New client instance SmtpClient.sys.mjs:121:17 14:19:37.716 mailnews.smtp: Connecting to smtp://smtp.comcast.net:587 SmtpClient.sys.mjs:141:19 14:19:37.799 mailnews.smtp: Connected SmtpClient.sys.mjs:429:17 14:20:39.211 mailnews.smtp: NetworkError: a Network error occurred SmtpClient.sys.mjs:476:17
_onError resource:///modules/SmtpClient.sys.mjs:476
14:20:39.212 mailnews.smtp: Socket closed. SmtpClient.sys.mjs:550:17 14:20:39.214 mailnews.smtp: SecurityError info: PR_END_OF_FILE_ERROR SmtpClient.sys.mjs:491:21 14:20:39.245 mailnews.send: Sending failed; The message could not be sent because the connection to Outgoing server (SMTP) smtp.comcast.net timed out. Try again., exitCode=2152398868, originalMsgURI=imap-message://mgiul%40comcast.net@imap.comcast.net/Drafts#57692 MessageSend.sys.mjs:343:32
smtp.comcast.net is using a self-signed cert. Is this the problem? C:\Users\rchar>openssl s_client -starttls smtp -connect smtp.comcast.net:587 Connecting to 96.103.145.180 CONNECTED(000001F8) depth=3 C=GB, ST=Greater Manchester, L=Salford, O=Comodo CA Limited, CN=AAA Certificate Services verify error:num=19:self-signed certificate in certificate chain verify return:1 depth=3 C=GB, ST=Greater Manchester, L=Salford, O=Comodo CA Limited, CN=AAA Certificate Services verify return:1 depth=2 C=GB, ST=Greater Manchester, L=Salford, O=COMODO CA Limited, CN=COMODO RSA Certification Authority verify return:1 depth=1 C=GB, ST=Greater Manchester, L=Salford, O=COMODO CA Limited, CN=COMODO RSA Organization Validation Secure Server CA verify return:1 depth=0 C=US, ST=Pennsylvania, O=Comcast Corporation, CN=smtp.comcast.net verify return:1 --- Certificate chain
0 s:C=US, ST=Pennsylvania, O=Comcast Corporation, CN=smtp.comcast.net i:C=GB, ST=Greater Manchester, L=Salford, O=COMODO CA Limited, CN=COMODO RSA Organization Validation Secure Server CA a:PKEY: RSA, 2048 (bit); sigalg: sha256WithRSAEncryption v:NotBefore: Jan 6 00:00:00 2025 GMT; NotAfter: Jan 6 23:59:59 2026 GMT 1 s:C=GB, ST=Greater Manchester, L=Salford, O=COMODO CA Limited, CN=COMODO RSA Organization Validation Secure Server CA i:C=GB, ST=Greater Manchester, L=Salford, O=COMODO CA Limited, CN=COMODO RSA Certification Authority a:PKEY: RSA, 2048 (bit); sigalg: sha384WithRSAEncryption v:NotBefore: Feb 12 00:00:00 2014 GMT; NotAfter: Feb 11 23:59:59 2029 GMT 2 s:C=GB, ST=Greater Manchester, L=Salford, O=COMODO CA Limited, CN=COMODO RSA Certification Authority i:C=GB, ST=Greater Manchester, L=Salford, O=Comodo CA Limited, CN=AAA Certificate Services a:PKEY: RSA, 4096 (bit); sigalg: sha384WithRSAEncryption v:NotBefore: Jan 1 00:00:00 2004 GMT; NotAfter: Dec 31 23:59:59 2028 GMT 3 s:C=GB, ST=Greater Manchester, L=Salford, O=Comodo CA Limited, CN=AAA Certificate Services i:C=GB, ST=Greater Manchester, L=Salford, O=Comodo CA Limited, CN=AAA Certificate Services a:PKEY: RSA, 2048 (bit); sigalg: sha1WithRSAEncryption v:NotBefore: Jan 1 00:00:00 2004 GMT; NotAfter: Dec 31 23:59:59 2028 GMT
--- Server certificate
BEGIN CERTIFICATE-----
MIIHATCCBemgAwIBAgIRAJUASDPOQisnR1zo9CfhXcYwDQYJKoZIhvcNAQELBQAw gZYxCzAJBgNVBAYTAkdCMRswGQYDVQQIExJHcmVhdGVyIE1hbmNoZXN0ZXIxEDAO BgNVBAcTB1NhbGZvcmQxGjAYBgNVBAoTEUNPTU9ETyBDQSBMaW1pdGVkMTwwOgYD VQQDEzNDT01PRE8gUlNBIE9yZ2FuaXphdGlvbiBWYWxpZGF0aW9uIFNlY3VyZSBT ZXJ2ZXIgQ0EwHhcNMjUwMTA2MDAwMDAwWhcNMjYwMTA2MjM1OTU5WjBdMQswCQYD VQQGEwJVUzEVMBMGA1UECBMMUGVubnN5bHZhbmlhMRwwGgYDVQQKExNDb21jYXN0 IENvcnBvcmF0aW9uMRkwFwYDVQQDExBzbXRwLmNvbWNhc3QubmV0MIIBIjANBgkq hkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAoLkgKQUqw4MylCObwwzTyFkIoMN/NRNl 6EY0zS+sjlYMFPplSULdfqs1tEcWZhCs+u1EkJN9+/juCtzeZ9c73yx8nTph0/KZ 5ri9t55yu5xhtuDv2WsMJmqcTOHPXRSZt7abpsvNfxCb6IG2YdPrBNqPyZPEJ6jn h3CY3qBbsreL4iR+UEGunSJAg2mRXHhx0/aYN3CTUetOcSBzIwoFXPklptWCcm5V knK+BWqFtKlyt6nHW/o2qK74nLDgKNUgxR9pG/Bw48ZER1emGsNlN2RVyOBtoAAG 15x4vD2iFBVEe9A0q9HOJc9bGSNb6zuU4ZpCb+RpNq3kkqJCpS6aJwIDAQABo4ID gDCCA3wwHwYDVR0jBBgwFoAUmvMr2s+tT7YvuypISCoStxtCwSQwHQYDVR0OBBYE FHz0nGUjqJ0rg0OQFz/hLkJ581OVMA4GA1UdDwEB/wQEAwIFoDAMBgNVHRMBAf8E AjAAMB0GA1UdJQQWMBQGCCsGAQUFBwMBBggrBgEFBQcDAjBKBgNVHSAEQzBBMDUG DCsGAQQBsjEBAgEDBDAlMCMGCCsGAQUFBwIBFhdodHRwczovL3NlY3RpZ28uY29t L0NQUzAIBgZngQwBAgIwWgYDVR0fBFMwUTBPoE2gS4ZJaHR0cDovL2NybC5jb21v ZG9jYS5jb20vQ09NT0RPUlNBT3JnYW5pemF0aW9uVmFsaWRhdGlvblNlY3VyZVNl cnZlckNBLmNybDCBiwYIKwYBBQUHAQEEfzB9MFUGCCsGAQUFBzAChklodHRwOi8v Y3J0LmNvbW9kb2NhLmNvbS9DT01PRE9SU0FPcmdhbml6YXRpb25WYWxpZGF0aW9u U2VjdXJlU2VydmVyQ0EuY3J0MCQGCCsGAQUFBzABhhhodHRwOi8vb2NzcC5jb21v ZG9jYS5jb20wggGABgorBgEEAdZ5AgQCBIIBcASCAWwBagB2AJaXZL9VWJet90OH aDcIQnfp8DrV9qTzNm5GpD8PyqnGAAABlDwZ58gAAAQDAEcwRQIhAOgI6NbRS4t6 9XvPVbmFixPHyFJXDqU60dv5r+RB9Y9YAiAwlfQhXe45ccND3T5te2KryuxvRhzW aBO3oIS6ixw6DAB3ABmG1Mcoqm/+ugNveCpNAZGqzi1yMQ+uzl1wQS0lTMfUAAAB lDwZ56oAAAQDAEgwRgIhAKmynGx19jBgk4Xy/eChCKjR/vpOtCH16470/jJyY6Yy AiEAkwlRN7Cn1AN20CGjNowsJ2PBaqNOk/u297W/RttgBKMAdwDLOPcViXyEoURf W8Hd+8lu8ppZzUcKaQWFsMsUwxRY5wAAAZQ8GefaAAAEAwBIMEYCIQDyR2Zz3Spd 0Gul6Z2dJa15aUEiEaW7KEAtbCcqz/zoLwIhAIV8YxWeI8rVaAvdl9kWquejUOTx M2G4iYjeZINb1VMgMEMGA1UdEQQ8MDqCEHNtdHAuY29tY2FzdC5uZXSCEHNtdHAu eGZpbml0eS5jb22CFHd3dy5zbXRwLmNvbWNhc3QubmV0MA0GCSqGSIb3DQEBCwUA A4IBAQBgn3Z51e8DZ/bO/AFqc22A4e5EqfUx4y6itcaz3mnQcU9pAsA/LK/WeY+e PtHIkWNKFlysJSbU2ByJ/6+bnebalXgRZ3sAeB2Z7UIUIHEjhcEQE2s4CxAXBiI7 SgqWjrw/Qj+AOghhMwayhIjmnNk34MmyY4f9KsAC6fIEn9ypCxuaN4lrwZcmS8iK o6PRho6pd837BEaRNIZBQpI/8WKxoKsNOu8bw8FwX/Zn8q+1oPo+0sQkmSmWOruu l8tlq8boA5R6YSBWek8hxmEZppvBs55wfNCnr2DQ4CgAREJZMKt6PIiKlgQ9r58b OSb5otnW7xsrx3SKM2zlvRA5mhfL
END CERTIFICATE-----
subject=C=US, ST=Pennsylvania, O=Comcast Corporation, CN=smtp.comcast.net issuer=C=GB, ST=Greater Manchester, L=Salford, O=COMODO CA Limited, CN=COMODO RSA Organization Validation Secure Server CA --- No client certificate CA names sent Peer signing digest: SHA256 Peer signature type: rsa_pss_rsae_sha256 Peer Temp Key: X25519, 253 bits --- SSL handshake has read 6708 bytes and written 1662 bytes Verification error: self-signed certificate in certificate chain --- New, TLSv1.3, Cipher is TLS_AES_256_GCM_SHA384 Protocol: TLSv1.3 Server public key is 2048 bit This TLS version forbids renegotiation. Compression: NONE Expansion: NONE No ALPN negotiated Early data was not sent Verify return code: 19 (self-signed certificate in certificate chain) --- 250 OK --- Post-Handshake New Session Ticket arrived: SSL-Session:
Protocol : TLSv1.3
Cipher : TLS_AES_256_GCM_SHA384
Session-ID: 27FBCE0D025BF752A9F038657257E923F1E5560B92BB78A47C5C9E0FFFDBEF7B
Session-ID-ctx:
Resumption PSK: FAFF92690FBEDF157D2856329FDABB033F2A0948C5A0F668E4B69C197EC6E52B8DE8A676EA4A78EAEEED7E90C4935DEC
PSK identity: None
PSK identity hint: None
SRP username: None
TLS session ticket lifetime hint: 300 (seconds)
TLS session ticket:
0000 - 97 cc 16 34 49 69 e3 c2-8f 6b ab cb e0 53 cb c1 ...4Ii...k...S..
0010 - e0 31 10 bf c8 94 c5 d1-59 2b 3e 84 f7 63 44 be .1......Y+>..cD.
0020 - 3e d6 69 b0 d4 10 7a 1a-4f 6a da 21 91 6b 34 f2 >.i...z.Oj.!.k4.
0030 - 1c 2c df cc 5f ee b5 ce-4c 71 49 b0 28 d6 7b 92 .,.._...LqI.(.{.
0040 - 9e 6a dd bb 93 ca 9e 44-80 1f df ec f7 e4 95 04 .j.....D........
0050 - 7c c1 6b 1d 86 59 7c 18-7d 98 41 0d 04 a1 f1 ae |.k..Y|.}.A.....
0060 - 7b 6d 68 ad 68 a6 b2 32-95 71 d3 89 09 ea 28 7c {mh.h..2.q....(|
0070 - ee 8f 67 1e ab e6 09 d7-5d c6 67 0d 0e 63 7b 24 ..g.....].g..c{$
0080 - 87 cc fb eb 8f a8 c6 67-60 d2 70 e6 58 93 06 d0 .......g`.p.X...
0090 - 1f ef 95 15 53 92 95 19-85 76 91 26 7c a1 9e 96 ....S....v.&|...
00a0 - 12 9d bd b2 a9 38 45 05-a5 28 14 65 4c ac c0 6d .....8E..(.eL..m
00b0 - c6 65 e7 b8 4b ff 0c dd-58 82 c9 c5 de 8d 64 ab .e..K...X.....d.
00c0 - f4 59 c5 5c bc bd c2 e9-34 2a d7 a7 99 21 97 60 .Y.\....4*...!.`
Start Time: 1756752732 Timeout : 7200 (sec) Verify return code: 19 (self-signed certificate in certificate chain) Extended master secret: no Max Early Data: 0
--- read R BLOCK --- Post-Handshake New Session Ticket arrived: SSL-Session:
Protocol : TLSv1.3
Cipher : TLS_AES_256_GCM_SHA384
Session-ID: 13DA31F60D1C9A3207FFEA54D2CEC29BB0D44016068E3E79A18492F695B02E80
Session-ID-ctx:
Resumption PSK: 44D18B4AEB19CDEBA968E3BD867C3B0167C07C61DC3091072882660FC234D4B3B071B663546C5B4AC3E53A6A5C206A9B
PSK identity: None
PSK identity hint: None
SRP username: None
TLS session ticket lifetime hint: 300 (seconds)
TLS session ticket:
0000 - 97 cc 16 34 49 69 e3 c2-8f 6b ab cb e0 53 cb c1 ...4Ii...k...S..
0010 - 09 52 42 f9 c9 f7 bc 99-5a b5 73 e3 9b b8 1c 91 .RB.....Z.s.....
0020 - 16 f5 ea 33 20 29 e1 59-79 65 46 0a 4b ad b7 fe ...3 ).YyeF.K...
0030 - b4 aa b7 7b f8 57 36 10-71 09 19 c6 d2 64 c4 8a ...{.W6.q....d..
0040 - 47 f6 28 4b 62 9e be ca-d9 16 1a e7 df 7d 51 f7 G.(Kb........}Q.
0050 - f6 66 04 fe 37 cf 0c bb-4f d8 d3 1b d6 06 be d0 .f..7...O.......
0060 - 21 ee 9e 65 ac a3 18 80-31 b7 17 5b 23 d2 9d 4e !..e....1..[#..N
0070 - 57 f7 b0 66 01 5f cc c5-a1 a5 96 ee d2 d8 55 ed W..f._........U.
0080 - 5b 91 86 da 91 d5 3d 17-36 bd a5 97 58 ab fb ad [.....=.6...X...
0090 - eb eb 38 5e fd e3 7a 13-b9 f8 5c 14 f5 80 3a 72 ..8^..z...\...:r
00a0 - 52 66 d9 23 8c a3 50 5c-3c e5 fc cb 22 21 11 3f Rf.#..P\<..."!.?
00b0 - a6 71 87 67 8b 33 8e b0-0a 65 46 f6 df 7a f0 f3 .q.g.3...eF..z..
00c0 - 04 4e cf 22 ad 4d 45 69-53 9c 45 56 df 07 ae e3 .N.".MEiS.EV....
Start Time: 1756752732 Timeout : 7200 (sec) Verify return code: 19 (self-signed certificate in certificate chain) Extended master secret: no Max Early Data: 0
--- read R BLOCK closed
C:\Users\rchar>
Chosen solution
Works today. <shrug> My settings:
Server Name: smtp.comcast.net Port: 587 User Name: <my email address> Authentication method: Normal password Connection Security: STARTTLS
Read this answer in context 👍 0All Replies (4)
Sometimes, it helps to post screenshot of the smtp server settings pane so others might offer suggestions.
The settings are not the issue, as they work with other clients (as noted in OP).
david said
Sometimes, it helps to post screenshot of the smtp server settings pane so others might offer suggestions.
I don't see where you mention that the settings work with other clients.
My working Comcast SMTP settings are:
Description: Comcast SMTP Server Name: smtp.comcast.net Port: 465 User Name: <my email address> Authentication method: Normal password Connection Security: SSL/TLS
=
As you may know, Comcast will soon, or maybe already has started to transition their mail service to Yahoo. I have received no official instructions from them about this yet, but maybe you're caught in the process.
Chosen Solution
Works today. <shrug> My settings:
Server Name: smtp.comcast.net Port: 587 User Name: <my email address> Authentication method: Normal password Connection Security: STARTTLS
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