Captive Portals are those redirect pages you get when you first use the internet connection at an airport or hotel or public wifi spot. Often a captive portal is requesting agreement to a Terms of Service and/or payment for usage.
Thunderbird doesn't currently detect Captive Portals well because they are designed to redirect web HTTP traffic and not mail SMTP/POP/IMAP. So if you aren't using a web browser Thunderbird appears to not be able to connect to your email and until you browse the web you won't know why.
This is a standard system for detecting captive portals, send a request to a known location and watch to see if you are redirected.
- On startup or when the network connection goes online: Open a hidden tab in the background
- The tab is going to a known location and will show itself if it gets redirected before reaching it's known location
git clone https://firstname.lastname@example.org/clarkbw/Thunderbird-Captive-Portal-Detector.git
pwd > tbcaptiveportaldetector@momo
mv tbcaptiveportaldetector@momo "YOUR THUNDERBIRD PROFILE DIRECTORY"
- Start Thunderbird
If you find a problem or a captive portal that wasn't detected correctly please file an issue in the github issue tracker. When filing please include the location and if possible the source code and URL of the problem portal page.