This site will have limited functionality while we undergo maintenance to improve your experience. If an article doesn't solve your issue and you want to ask a question, we have our support community waiting to help you at @FirefoxSupport on Twitter and/r/firefox on Reddit.

Avoid support scams. We will never ask you to call or text a phone number or share personal information. Please report suspicious activity using the “Report Abuse” option.

Learn More

Keep getting error msg "Sending of username did not succeed. Mail server mail.comcast.net responded: [AUTH] Authentication failed."

Out of the blue, I am getting error msg every time I open Thunderbird:

          Sending of username did not succeed. Mail server mail.comcast.net responded: [AUTH] Authentication failed.

When I click on OK, I get another message:

Login Failed Login to server mail.comcast.net failed. Enter New Password Cancel Retry

I've tried resetting my password but it hasn't helped. I am NOT computer savvy, so please make any suggested fixes as simple as possible. Many thanks!

Out of the blue, I am getting error msg every time I open Thunderbird: Sending of username did not succeed. Mail server mail.comcast.net responded: [AUTH] Authentication failed. When I click on OK, I get another message: Login Failed Login to server mail.comcast.net failed. Enter New Password Cancel Retry I've tried resetting my password but it hasn't helped. I am NOT computer savvy, so please make any suggested fixes as simple as possible. Many thanks!

All Replies (6)

Go to the Help Menu in Thunderbird. Click Troubleshooting Information. Click Copy to Clipboard Come back here and paste that info into a reply window.

If it errors out as too much info, delete the font and printer info. It is not needed for this issue anyway.

Application Basics

   Name: Thunderbird
   Version: 52.4.0
   User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.11; rv:52.0) Gecko/20100101 Thunderbird/52.4.0
   Profile Folder: Show in Finder
   Application Build ID: 20171004092449
   Enabled Plugins: about:plugins
   Build Configuration: about:buildconfig
   Memory Use: about:memory
   Profiles: about:profiles
 Mail and News Accounts
   account1:
     INCOMING: account1, , (none) Local Folders, plain, passwordCleartext
   account2:
     INCOMING: account2, , (pop3) mail.comcast.net:110, plain, passwordCleartext
     OUTGOING: , smtp.comcast.net:587, plain, passwordCleartext, true
   account3:
     INCOMING: account3, , (imap) imap.googlemail.com:993, SSL, passwordCleartext
     OUTGOING: , smtp.googlemail.com:465, SSL, passwordCleartext, true
   account4:
     INCOMING: account4, , (pop3) mail.comcast.net:995, SSL, passwordCleartext
     OUTGOING: , smtp.comcast.net:587, alwaysSTARTTLS, passwordCleartext, true
 Crash Reports
   https://crash-stats.mozilla.com/report/index/bp-35408fe4-95df-4f60-952a-df80c2170306 (3/6/17)
   https://crash-stats.mozilla.com/report/index/bp-2d253d6a-9c53-4a64-8d29-c19862150923 (9/23/15)
   https://crash-stats.mozilla.com/report/index/bp-4536204a-be86-4e45-99e0-72e442140512 (5/12/14)
   https://crash-stats.mozilla.com/report/index/bp-1eb2b8e4-ca80-4c0b-8677-b41372140320 (3/20/14)
   https://crash-stats.mozilla.com/report/index/bp-a554a3a1-1ec9-4341-805b-05de22130704 (7/3/13)
 Extensions
   Lightning, 5.4.4, true, {e2fda1a4-762b-4020-b5ad-a41df1933103}
 Important Modified Preferences
   Name: Value
     accessibility.typeaheadfind.flashBar: 0
     browser.cache.disk.capacity: 358400
     browser.cache.disk.filesystem_reported: 1
     browser.cache.disk.smart_size_cached_value: 358400
     browser.cache.disk.smart_size.first_run: false
     browser.cache.disk.smart_size.use_old_max: false
     extensions.lastAppVersion: 52.4.0
     font.internaluseonly.changed: true
     mail.openMessageBehavior.version: 1
     mail.spotlight.firstRunDone: true
     mailnews.database.global.datastore.id: ebe1589e-4c90-a148-aa38-1d55726823e
     mailnews.database.global.views.conversation.columns: {"threadCol":{"visible":true,"ordinal":"1"},"flaggedCol":{"visible":true,"ordinal":"21"},"attachmentCol":{"visible":fals…
     mailnews.database.global.views.global.columns: {"threadCol":{"visible":true,"ordinal":"1"},"flaggedCol":{"visible":true,"ordinal":"21"},"attachmentCol":{"visible":fals…
     media.gmp.storage.version.observed: 1
     network.cookie.cookieBehavior: 3
     network.cookie.lifetimePolicy: 1
     network.cookie.prefsMigrated: true
     network.predictor.cleaned-up: true
     places.database.lastMaintenance: 1511890052
     places.history.expiration.transient_current_max_pages: 56812
     plugin.disable_full_page_plugin_for_types: video/x-ms-wmv
     plugin.importedState: true
     print.macosx.pagesetup: PD94bWwgdmVyc2lvbj0iMS4wIiBlbmNvZGluZz0iVVRGLTgiPz4KPCFET0NUWVBFIHBsaXN0IFBVQkxJQyAiLS8vQXBwbGUgQ29tcHV0ZXIvL0RURCBQTElT…
     print.macosx.pagesetup-2: PD94bWwgdmVyc2lvbj0iMS4wIiBlbmNvZGluZz0iVVRGLTgiPz4KPCFET0NUWVBFIHBsaXN0IFBVQkxJQyAiLS8vQXBwbGUvL0RURCBQTElTVCAxLjAvL0VO…
     print.print_bgcolor: false
     print.print_bgimages: false
     print.print_command:
     print.print_downloadfonts: true
     print.print_evenpages: true
     print.print_in_color: true
     print.print_margin_bottom: 0.5
     print.print_margin_left: 0.5
     print.print_margin_right: 0.5
     print.print_margin_top: 0.5
     print.print_oddpages: true
     print.print_orientation: 0
     print.print_pagedelay: 500
     print.print_paper_data: 0
     print.print_paper_height: 11.00
     print.print_paper_size: 6619250
     print.print_paper_size_type: 1
     print.print_paper_size_unit: 0
     print.print_paper_width: 8.50
     print.print_printer:
     print.print_reversed: false
     print.print_scaling: 1.00
     print.print_shrink_to_fit: true
     print.print_to_file: false
     print.print_unwriteable_margin_bottom: 56
     print.print_unwriteable_margin_left: 25
     print.print_unwriteable_margin_right: 25
     print.print_unwriteable_margin_top: 25
     privacy.donottrackheader.enabled: true
     security.sandbox.content.tempDirSuffix: {ac4515f1-4163-ae4d-8a57-feed2400d6f2}
 Graphics
     GPU #1
     Vendor ID: 0x10de
     Device ID: 0x0fea
     Features
     WebGL Renderer: NVIDIA Corporation -- NVIDIA GeForce GT 755M OpenGL Engine -- 2.1 NVIDIA-10.10.14 310.42.25f02
     AzureCanvasBackend: skia
     AzureCanvasAccelerated: 0
     AzureFallbackCanvasBackend: none
     AzureContentBackend: skia
     TileHeight: 1024
     TileWidth: 1024
 JavaScript
 Incremental GC: 1
 Accessibility
   Activated: 0
   Prevent Accessibility: 0
 Library Versions
     Expected minimum version
     Version in use
     NSPR
     4.13.1
     4.13.1
     NSS
     3.28.6
     3.28.6
     NSS Util
     3.28.6
     3.28.6
     NSS SSL
     3.28.6
     3.28.6
     NSS S/MIME
     3.28.6
     3.28.6

It is your account #2 as listed in your Troubleshooting Info. You are using the unsecure port of 110 and no Authentication just like the error message states.

Change those server settings to: Port 995 - SSL/TLS - Normal Password for the POP server Port 465 - SSL/TLS - Normal Password for the SMTP server

To do this right click the account in the Folder Pane on the left side and select Settings. The POP settings are in Server Settings. To change the SMTP settings go to the very bottom of the list in the Settings screen and click Outgoing Server (SMTP) Select the incorrect account and select Edit

Thank you so much for the timely replies. Unfortunately, making those settings changes (see images) didn't fix it. I'm still getting error messages. Here's the current troubleshooting information (after I made the changes):


 Application Basics
   Name: Thunderbird
   Version: 52.4.0
   User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.11; rv:52.0) Gecko/20100101 Thunderbird/52.4.0
   Profile Folder: Show in Finder
   Application Build ID: 20171004092449
   Enabled Plugins: about:plugins
   Build Configuration: about:buildconfig
   Memory Use: about:memory
   Profiles: about:profiles
 Mail and News Accounts
   account1:
     INCOMING: account1, , (none) Local Folders, plain, passwordCleartext
   account2:
     INCOMING: account2, , (pop3) mail.comcast.net:995, SSL, passwordCleartext
     OUTGOING: , smtp.comcast.net:465, SSL, passwordCleartext, true
   account3:
     INCOMING: account3, , (imap) imap.googlemail.com:993, SSL, passwordCleartext
     OUTGOING: , smtp.googlemail.com:465, SSL, passwordCleartext, true
   account4:
     INCOMING: account4, , (pop3) mail.comcast.net:995, SSL, passwordCleartext
     OUTGOING: , smtp.comcast.net:465, SSL, passwordCleartext, true
 Crash Reports
   https://crash-stats.mozilla.com/report/index/bp-35408fe4-95df-4f60-952a-df80c2170306 (3/6/17)
   https://crash-stats.mozilla.com/report/index/bp-2d253d6a-9c53-4a64-8d29-c19862150923 (9/23/15)
   https://crash-stats.mozilla.com/report/index/bp-4536204a-be86-4e45-99e0-72e442140512 (5/12/14)
   https://crash-stats.mozilla.com/report/index/bp-1eb2b8e4-ca80-4c0b-8677-b41372140320 (3/20/14)
   https://crash-stats.mozilla.com/report/index/bp-a554a3a1-1ec9-4341-805b-05de22130704 (7/3/13)
 Extensions
   Lightning, 5.4.4, true, {e2fda1a4-762b-4020-b5ad-a41df1933103}
 Important Modified Preferences
   Name: Value
     accessibility.typeaheadfind.flashBar: 0
     browser.cache.disk.capacity: 358400
     browser.cache.disk.filesystem_reported: 1
     browser.cache.disk.smart_size_cached_value: 358400
     browser.cache.disk.smart_size.first_run: false
     browser.cache.disk.smart_size.use_old_max: false
     extensions.lastAppVersion: 52.4.0
     font.internaluseonly.changed: true
     mail.openMessageBehavior.version: 1
     mail.spotlight.firstRunDone: true
     mailnews.database.global.datastore.id: ebe1589e-4c90-a148-aa38-1d55726823e
     mailnews.database.global.views.conversation.columns: {"threadCol":{"visible":true,"ordinal":"1"},"flaggedCol":{"visible":true,"ordinal":"21"},"attachmentCol":{"visible":fals…
     mailnews.database.global.views.global.columns: {"threadCol":{"visible":true,"ordinal":"1"},"flaggedCol":{"visible":true,"ordinal":"21"},"attachmentCol":{"visible":fals…
     media.gmp.storage.version.observed: 1
     network.cookie.cookieBehavior: 3
     network.cookie.lifetimePolicy: 1
     network.cookie.prefsMigrated: true
     network.predictor.cleaned-up: true
     places.database.lastMaintenance: 1511890052
     places.history.expiration.transient_current_max_pages: 56812
     plugin.disable_full_page_plugin_for_types: video/x-ms-wmv
     plugin.importedState: true
     print.macosx.pagesetup: PD94bWwgdmVyc2lvbj0iMS4wIiBlbmNvZGluZz0iVVRGLTgiPz4KPCFET0NUWVBFIHBsaXN0IFBVQkxJQyAiLS8vQXBwbGUgQ29tcHV0ZXIvL0RURCBQTElT…
     print.macosx.pagesetup-2: PD94bWwgdmVyc2lvbj0iMS4wIiBlbmNvZGluZz0iVVRGLTgiPz4KPCFET0NUWVBFIHBsaXN0IFBVQkxJQyAiLS8vQXBwbGUvL0RURCBQTElTVCAxLjAvL0VO…
     print.print_bgcolor: false
     print.print_bgimages: false
     print.print_command:
     print.print_downloadfonts: true
     print.print_evenpages: true
     print.print_in_color: true
     print.print_margin_bottom: 0.5
     print.print_margin_left: 0.5
     print.print_margin_right: 0.5
     print.print_margin_top: 0.5
     print.print_oddpages: true
     print.print_orientation: 0
     print.print_pagedelay: 500
     print.print_paper_data: 0
     print.print_paper_height: 11.00
     print.print_paper_size: 6619250
     print.print_paper_size_type: 1
     print.print_paper_size_unit: 0
     print.print_paper_width: 8.50
     print.print_printer:
     print.print_reversed: false
     print.print_scaling: 1.00
     print.print_shrink_to_fit: true
     print.print_to_file: false
     print.print_unwriteable_margin_bottom: 56
     print.print_unwriteable_margin_left: 25
     print.print_unwriteable_margin_right: 25
     print.print_unwriteable_margin_top: 25
     privacy.donottrackheader.enabled: true
     security.sandbox.content.tempDirSuffix: {ac4515f1-4163-ae4d-8a57-feed2400d6f2}
 Graphics
     GPU #1
     Vendor ID: 0x10de
     Device ID: 0x0fea
     Features
     WebGL Renderer: NVIDIA Corporation -- NVIDIA GeForce GT 755M OpenGL Engine -- 2.1 NVIDIA-10.10.14 310.42.25f02
     AzureCanvasBackend: skia
     AzureCanvasAccelerated: 0
     AzureFallbackCanvasBackend: none
     AzureContentBackend: skia
     TileHeight: 1024
     TileWidth: 1024
 JavaScript
 Incremental GC: 1
 Accessibility
   Activated: 0
   Prevent Accessibility: 0
 Library Versions
     Expected minimum version
     Version in use
     NSPR
     4.13.1
     4.13.1
     NSS
     3.28.6
     3.28.6
     NSS Util
     3.28.6
     3.28.6
     NSS SSL
     3.28.6
     3.28.6
     NSS S/MIME
     3.28.6
     3.28.6

Please ignore the "see images" above.

You could try switching your SMTP settings back to the way account 4 was in your original info. Here is the Comcast page for their settings and they say use 587 as first choice. I use 465 with no issues. https://www.xfinity.com/support/internet/email-client-programs-with-xfinity-email/