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Connection Timeout and SMTP Failure Issues

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Dear Thunderbird Technical Support,

I hope this email finds you well. I am reaching out to seek assistance with two recurring problems I have been experiencing while using Thunderbird as my email client. I have encountered connection timeout issues with both Gmail and our company's website servers, as well as SMTP failures when attempting to send emails. I would greatly appreciate your guidance and support in resolving these matters.

Here are the specific details regarding my setup and configurations:

SMTP Configuration: Server Name: smtp.gmail.com Port: 465 Connection Security: SSL/TLS Authentication Method: OAuth2

While using Thunderbird, I am connected to the internet through VPN V2RAYN. However, despite configuring the SMTP settings as provided above, I am facing difficulties with both connection timeouts and failures when attempting to send emails.

I kindly request your assistance in troubleshooting these issues and providing any necessary steps or recommendations to resolve them. It is crucial for me to have a reliable email client, as efficient communication is essential for my work.

If you require any additional information or logs, please let me know, and I will be more than happy to provide them promptly. I understand that resolving these technical issues may require your expertise, and I appreciate your time and attention to this matter.

Thank you for your assistance. I look forward to your prompt response and guidance.

Best regards,

Dear Thunderbird Technical Support, I hope this email finds you well. I am reaching out to seek assistance with two recurring problems I have been experiencing while using Thunderbird as my email client. I have encountered connection timeout issues with both Gmail and our company's website servers, as well as SMTP failures when attempting to send emails. I would greatly appreciate your guidance and support in resolving these matters. Here are the specific details regarding my setup and configurations: SMTP Configuration: Server Name: smtp.gmail.com Port: 465 Connection Security: SSL/TLS Authentication Method: OAuth2 While using Thunderbird, I am connected to the internet through VPN V2RAYN. However, despite configuring the SMTP settings as provided above, I am facing difficulties with both connection timeouts and failures when attempting to send emails. I kindly request your assistance in troubleshooting these issues and providing any necessary steps or recommendations to resolve them. It is crucial for me to have a reliable email client, as efficient communication is essential for my work. If you require any additional information or logs, please let me know, and I will be more than happy to provide them promptly. I understand that resolving these technical issues may require your expertise, and I appreciate your time and attention to this matter. Thank you for your assistance. I look forward to your prompt response and guidance. Best regards,

All Replies (20)

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Just to clarify: do these problems exist when you are not using the VPN? I ask that because VPN use is often the reason for problems such as you describe.

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Yes, as my questions was asked this way : While using Thunderbird, I am connected to the internet through VPN.

Modified by pj.group.com

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Does the problem go away when you do not use the VPN?

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if I don't use VPN, I cannot even connect at all...

Modified by pj.group.com

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Check your internet connection: Ensure that you have a stable and working internet connection. Try accessing other websites or online services to verify your internet connectivity.

Disable antivirus/firewall: Temporarily disable your antivirus software or firewall to see if they are causing any conflicts with Thunderbird's connection. Sometimes, these security programs can interfere with email clients.

Verify server settings: Double-check that your server settings in Thunderbird are correct. Go to "Tools" (or "Options") > "Account Settings" and make sure the incoming and outgoing server settings (IMAP/POP and SMTP) are accurate. You may need to contact your email provider to obtain the correct server settings.

Regards, TG

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I am computer technician. To test the problem, I am using 3 different devices : 1. 2 Computers with Windows 7 64-bit with Thunderbird 102.12.0 (64-bit). 2. Samsung phone with Android and Gmail app

On both devices, I am using VPN.

I can always receive and send emails using Gmail app, never any problem.

Using the exactly same computer with same Windows, etc.. in Europe, I can send emails no problem, so the IMAP and SMTP are perfectly configured.

Since the computers are the same working perfectly well, and my phone can always send emails, there is a problem with Thunderbird handling the problem with mails servers, both Gmail and other servers.

Many server timeout, difficulty to load emails and sending emails.

But for a moment, Yesterday, I thought I have solved the problem by l imitating the number of server connection to cash to 2 instead of 5. Which worked perfectly on all emails addresses I did the change.

Then today, only Thunderbird has problems.

So I even changed the mailnews.tcptimeout to 1000000 as explained on the forums.

The problem, in my opinion comes from the way Thunderbird communicates with the servers and handles the communication. Gmail app works perfect.

Hope you can solve this.

Modified by pj.group.com

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Did you find a solution ? Just need Thunderbird to handle better the SMTP and time out issues... As the same phone with Gmail app doesn't have this problem.

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FRom a Thunderbird perspective Phone connectivity or gmail.app or webmail connectivity via a browser is not relevant except for proving the password is known and works on account.

re: While using Thunderbird, I am connected to the internet through VPN V2RAYN. However, despite configuring the SMTP settings as provided above, I am facing difficulties with both connection timeouts and failures when attempting to send emails. I am using VPN.

Thunderbird is a third party email client and alot of servers do not like people trying to connect to their servers via a third party app using a VPN because the server believes it could be someone trying to hide their IP address and that means the person trying to access the account may be a hacker. Basically server is not playing ball in order to preserve your privacy.

However, some people may be using a VPN but by using static IP get a better result. Others who want to use a VPN may have needed to set up a tunnel for Thunderbird to use. Generally the advise is do not use the VPN unless you are using a static IP. So, try to set up a static IP to use over VPN and see if it improves the situation.

The SMTP settings you posted are correct. It sounds like every so often you might get a connection and it works ok but it fails frequently. This implies server settings in Thunderbird are not the problem, otherwise you would have never got a connection to gmail via oauth.

To test they work correctly suggest you restart computer in 'safe node with networking' and do not use VPN. You will also need an ethernet cable to connect computer to router.

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pj.group.com are you still seeing a problem?

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Yes, the problem is still here and remains unsolved even after the Thunderbird updates.

I have been told there is a problem between Gmail and Thunderbird... Maybe Gmail wants to push for using the webmail but the webmail is very badly designed comparatively to the Thunderbird program.

Moreover, it is a problem to login and reply on this forum, to login, have to go to Firefox accounts then after log in, just land into a closet... can't reach in one click the forum and answer the questions, I have to google my own question and then need to log in again. Not easy at all, looks like 1990's way of entering the web... Sorry..

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Hi there! It sounds like you're facing some challenges with Thunderbird and Gmail connectivity. It's great that you're using Thunderbird as your email client, but sometimes VPN connections can cause issues with server connections. If you're using a VPN, try setting up a static IP to improve the situation. Also, ensure that your SMTP settings are correct, as you've mentioned. Gmail might have some compatibility issues with Thunderbird, but the webmail interface isn't as user-friendly. As for the forum login issue, it might be a technical glitch that could be looked into by the technical team. Hang in there, and keep exploring solutions for your Thunderbird connectivity.

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if I don't use VPN, I cannot even connect at all

You don't need a VPN to connect to Gmail.

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re :I have to google my own question: When you get an email because someone posted a comment in a question you created, you can use that email to open the question in a browser. There will be a button which you can clickon if answer solved question, but to the right of that button is some text - cannot remember what it says but it is a link to the question in forum.

You could just view your profile and see all the questions etc you created. Maybe set it up as bookmark. https://support.mozilla.org/en-US/user/pj.group.com/

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re :I have been told there is a problem between Gmail and Thunderbird.

I'm not having any issues. But there is usually a reason if a problem exists.

1. Firewall is set up to allow Thunderbird 2. Do NOT use VPN because gmail does not like it. If it gets various IP addresses it thinks you are a hacker and blocks the account. Expect problems if you use VPN - it's not Thunderbird who does not like it. Gmail server will block access. 3. Thunderbird Settings > Privacy & Security - select 'Accept cookies from sites' 4. If using a product which uses 'localhost' eg: Apache - switch it off when trying to create mail account or reset password as setting up oauth token needs to use locallost. 5. Use correct server settings. If using oauth then do not enable gmail 2 step authentication - do not use app generated password.

If using OAuth:

  • Imap: incoming server: imap.gmail.com
  • port: 993
  • Connection Security: SSL/TLS
  • Authentication Method: OAuth2
  • User name: full email address
  • Password: same one you use to access webmail
  • SMTP outgoing server: smtp.gmail.com
  • port: 465
  • Connection Security: SSL/TLS
  • Authentication Method: OAuth2
  • User name: full email address
  • Password: same one you use to access webmail

Normal webmail Password is only used when google ask for password to confirm you really are you and to allow Thunderbird access. At this point an oauth token is created and saved in Thunderbird. Then thunderbird uses token to get access. You never use token - only thunderbird.

IF you are NOT using Authentication Method: OAuth2:

  • In Google/gmail account set up to use 2step authentication and create an app specific password to use in Thunderbird.
  • Account server settings are the same except set 'Authentication Method: Normal Password' for incoming and outgoing server.
  • When prompted for password enter the app generated password.
  • Select checkbox to instruct Thunderbird to remember password.

Advise and this is also mentioned by gmail in their help pages - when setting up to check server for new mail - set 15 minutes or more - you may find you can set it up to be 30mins because you should find you get immediate notification when new mail arrives as gmail may push them.

Potential issues on access to server when using gmail which are controlled by gmail. Gmail server request limits: For the health and safety of our systems and your account, there’s a limit to the number of server requests a Gmail account can make at one time. When the limit is reached, the account is temporarily suspended. https://support.google.com/a/answer/1359240?hl=en

Important: To avoid temporarily locking yourself out of your account, make sure you don't exceed 2500 MB per day for IMAP downloads and 500 MB per day for IMAP uploads. If you're setting up a single IMAP account on multiple computers, try taking a break between each setup.


Gmail has limits on sending. You hit a limit and gmail will temp block access. You may have hit limits. Gmail limits on sending:

You can only use 15 IMAP connections per account. If you have many email clients getting messages from Gmail at the same time, you may see the "Too many simultaneous connections" error.

You can limit number of connections within Thunderbird to eg: 2 and it will help. BUT....be aware that the number of connections to server includes connections from all other devices including phone. Switch off phone to force those connections to close.

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christ1 said

if I don't use VPN, I cannot even connect at all

You don't need a VPN to connect to Gmail.

If I don't use VPN, I cannot connect to GMail BECAUSE GMail is banned in that country. I don't know what you cannot understand ?

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Toad-Hall said

re :I have been told there is a problem between Gmail and Thunderbird. I'm not having any issues. But there is usually a reason if a problem exists. 1. Firewall is set up to allow Thunderbird 2. Do NOT use VPN because gmail does not like it. If it gets various IP addresses it thinks you are a hacker and blocks the account. Expect problems if you use VPN - it's not Thunderbird who does not like it. Gmail server will block access. 3. Thunderbird Settings > Privacy & Security - select 'Accept cookies from sites' 4. If using a product which uses 'localhost' eg: Apache - switch it off when trying to create mail account or reset password as setting up oauth token needs to use locallost. 5. Use correct server settings. If using oauth then do not enable gmail 2 step authentication - do not use app generated password. If using OAuth:
  • Imap: incoming server: imap.gmail.com
  • port: 993
  • Connection Security: SSL/TLS
  • Authentication Method: OAuth2
  • User name: full email address
  • Password: same one you use to access webmail
  • SMTP outgoing server: smtp.gmail.com
  • port: 465
  • Connection Security: SSL/TLS
  • Authentication Method: OAuth2
  • User name: full email address
  • Password: same one you use to access webmail
Normal webmail Password is only used when google ask for password to confirm you really are you and to allow Thunderbird access. At this point an oauth token is created and saved in Thunderbird. Then thunderbird uses token to get access. You never use token - only thunderbird. IF you are NOT using Authentication Method: OAuth2:
  • In Google/gmail account set up to use 2step authentication and create an app specific password to use in Thunderbird.
  • Account server settings are the same except set 'Authentication Method: Normal Password' for incoming and outgoing server.
  • When prompted for password enter the app generated password.
  • Select checkbox to instruct Thunderbird to remember password.
Advise and this is also mentioned by gmail in their help pages - when setting up to check server for new mail - set 15 minutes or more - you may find you can set it up to be 30mins because you should find you get immediate notification when new mail arrives as gmail may push them. Potential issues on access to server when using gmail which are controlled by gmail. Gmail server request limits: For the health and safety of our systems and your account, there’s a limit to the number of server requests a Gmail account can make at one time. When the limit is reached, the account is temporarily suspended. https://support.google.com/a/answer/1359240?hl=en Important: To avoid temporarily locking yourself out of your account, make sure you don't exceed 2500 MB per day for IMAP downloads and 500 MB per day for IMAP uploads. If you're setting up a single IMAP account on multiple computers, try taking a break between each setup. Gmail has limits on sending. You hit a limit and gmail will temp block access. You may have hit limits. Gmail limits on sending: You can only use 15 IMAP connections per account. If you have many email clients getting messages from Gmail at the same time, you may see the "Too many simultaneous connections" error. You can limit number of connections within Thunderbird to eg: 2 and it will help. BUT....be aware that the number of connections to server includes connections from all other devices including phone. Switch off phone to force those connections to close.

If I don't use a VPN where GMail is banned, I cannot connect to GMail, please understand that.

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re :If I don't use a VPN where GMail is banned, I cannot connect to GMail, please understand that.

I now understand your problem. But this is the first time you have mentioned you are trying to access gmail from within a country that bans it. Are you able to set up vpn to use a static ip?

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pj.group.com said

Toad-Hall said

re :I have been told there is a problem between Gmail and Thunderbird. I'm not having any issues. But there is usually a reason if a problem exists. 1. Firewall is set up to allow Thunderbird 2. Do NOT use VPN because gmail does not like it. If it gets various IP addresses it thinks you are a hacker and blocks the account. Expect problems if you use VPN - it's not Thunderbird who does not like it. Gmail server will block access. 3. Thunderbird Settings > Privacy & Security - select 'Accept cookies from sites' 4. If using a product which uses 'localhost' eg: Apache - switch it off when trying to create mail account or reset password as setting up oauth token needs to use locallost. 5. Use correct server settings. If using oauth then do not enable gmail 2 step authentication - do not use app generated password. If using OAuth:
  • Imap: incoming server: imap.gmail.com
  • port: 993
  • Connection Security: SSL/TLS
  • Authentication Method: OAuth2
  • User name: full email address
  • Password: same one you use to access webmail
  • SMTP outgoing server: smtp.gmail.com
  • port: 465
  • Connection Security: SSL/TLS
  • Authentication Method: OAuth2
  • User name: full email address
  • Password: same one you use to access webmail
Normal webmail Password is only used when google ask for password to confirm you really are you and to allow Thunderbird access. At this point an oauth token is created and saved in Thunderbird. Then thunderbird uses token to get access. You never use token - only thunderbird. IF you are NOT using Authentication Method: OAuth2:
  • In Google/gmail account set up to use 2step authentication and create an app specific password to use in Thunderbird.
  • Account server settings are the same except set 'Authentication Method: Normal Password' for incoming and outgoing server.
  • When prompted for password enter the app generated password.
  • Select checkbox to instruct Thunderbird to remember password.
Advise and this is also mentioned by gmail in their help pages - when setting up to check server for new mail - set 15 minutes or more - you may find you can set it up to be 30mins because you should find you get immediate notification when new mail arrives as gmail may push them. Potential issues on access to server when using gmail which are controlled by gmail. Gmail server request limits: For the health and safety of our systems and your account, there’s a limit to the number of server requests a Gmail account can make at one time. When the limit is reached, the account is temporarily suspended. https://support.google.com/a/answer/1359240?hl=en Important: To avoid temporarily locking yourself out of your account, make sure you don't exceed 2500 MB per day for IMAP downloads and 500 MB per day for IMAP uploads. If you're setting up a single IMAP account on multiple computers, try taking a break between each setup. Gmail has limits on sending. You hit a limit and gmail will temp block access. You may have hit limits. Gmail limits on sending: You can only use 15 IMAP connections per account. If you have many email clients getting messages from Gmail at the same time, you may see the "Too many simultaneous connections" error. You can limit number of connections within Thunderbird to eg: 2 and it will help. BUT....be aware that the number of connections to server includes connections from all other devices including phone. Switch off phone to force those connections to close.

If I don't use a VPN where GMail is banned, I cannot connect to GMail, please understand that.

Already configurated correctly.

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Toad-Hall said

re :If I don't use a VPN where GMail is banned, I cannot connect to GMail, please understand that. I now understand your problem. But this is the first time you have mentioned you are trying to access gmail from within a country that bans it. Are you able to set up vpn to use a static ip?

Cannot get a static IP as the node would be discovered and under attack/deactivated/blocked.

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The Gmail app on smartphone at least works well, but it is on the phone, cannot work computer files on the phone. Thunderbird is far more superior than Gmail app and especially the webmail (which was designed by default for kids, not professional at all).

Since the Gmail app works very well using VPN and not a static IP, the problem comes from Thunderbird only.