I have an Outlook.com account that has worked flawlessly for well over a decade and it works easily with Thunderbird. Another strength of Outlook is that it has a please web interface for those times when you don't have Thunderbird available.

Thanks @david. Actually I was asking for experience with other providers besides Gmail and Outlook. Maybe I should edit my post. I also have a outlook account and I agree that it is far less problematic than gmail.

Okay, in that case, my primary email provider is netaddress.com . I've been with them for 20 years. It's not free, but it works and works well. And provides extra services, such as tasks, prewritten messages, spam filter, whitelisting, blacklisting, alias addresses, and I can even restore deleted messages, going back several weeks.

Thank you @david. I guess Mailfence should also be a good option since they have a partnership with Thunderbird.

re : I'm getting fed up with gmail because it keeps randomly not being able to send emails.

Previously, gmail used to periodically deliberately choose to block Pop accounts requiring a reset to use what gmail call 'less secure apps' option. Gmail did this to force you to use webmail login which they claimed was for your benefit as a security check. But gmail are about to switch that 'less secure apps' option off.

Is this a gmail pop or imap account ? Have you set up to allow cookies in Thunderbird and then changed the Account Settings Authentication Method for incoming and outgoing smtp to use OAuth2 ?

I do not have any issue with my imap gmail account. I also have an email address with my internet service provider (BT) using a POP account and have no problems.

Some people like GMX which is also a free email.

In my experience answering questions in this forum, people using yahoo servers often have issues or very old email addresses which have been passed on to other servers. Some still only offer insecure options.

Some servers are fine until you start travelling around and still try to connect which they may block as a security check.

Recently, yahoo, gmail and some others have been changing the way they allow third party email clients to access server and this had led to connection issues. Oauth is their prefered Authentication Method, but 2 step verification is available.

Some servers such as AOL are requesting the use 2 step verification and app specific passwords.

Xfinity (comcast) have introduced a new setting in the webmail account which requires people to select it to allow third party clients access. So when those using Xfinity suddenly get access issues, it's often because they have no idea about new changes Xfinity introduced.

However, in most cases, once people get their server settings updated to use the new Authentication Methods the connection issues are significantly reduced.

re : I'm getting fed up with gmail because it keeps randomly not being able to send emails. Previously, gmail used to periodically deliberately choose to block Pop accounts requiring a reset to use what gmail call 'less secure apps' option. Gmail did this to force you to use webmail login which they claimed was for your benefit as a security check. But gmail are about to switch that 'less secure apps' option off. Is this a gmail pop or imap account ? Have you set up to allow cookies in Thunderbird and then changed the Account Settings Authentication Method for incoming and outgoing smtp to use OAuth2 ? I do not have any issue with my imap gmail account. I also have an email address with my internet service provider (BT) using a POP account and have no problems. Some people like GMX which is also a free email. In my experience answering questions in this forum, people using yahoo servers often have issues or very old email addresses which have been passed on to other servers. Some still only offer insecure options. Some servers are fine until you start travelling around and still try to connect which they may block as a security check. Recently, yahoo, gmail and some others have been changing the way they allow third party email clients to access server and this had led to connection issues. Oauth is their prefered Authentication Method, but 2 step verification is available. Some servers such as AOL are requesting the use 2 step verification and app specific passwords. Xfinity (comcast) have introduced a new setting in the webmail account which requires people to select it to allow third party clients access. So when those using Xfinity suddenly get access issues, it's often because they have no idea about new changes Xfinity introduced. However, in most cases, once people get their server settings updated to use the new Authentication Methods the connection issues are significantly reduced.

Thanks for the answer. I'm using an imap account. This problem that I describe only happens in my Ubuntu system, my Manjaro one works fine.

This question arouse more because I wanted to know alternatives. I just think that Google tries to monopolize the market and sometimes it tries very hard to control the users. I just wanted to know alternatives for when I finally decide to stop using gmail as my main email.