Hello community. My company decided, right before Christmas, to force-migrate all e-mail addresses from the functioning old servers to "Exchange Online", which not only made the web-browser based access more complicated, but also required changes in Thunderbird. While they provided instructions, which I slavishly followed (despite being usually rather hand around the computer), I still cannot send e-mails with my work address - they get timed out. My company IT are notoriously unwilling to help with issues on the private computer and have recommended even beforehand to from now on only use the web-based access to avoid trouble - which is laughable, for me, as I need my e-mails offline as well. So before harassing them more loudly, I wanted to make sure it's a fault on their end not on mine. Some details: New server is outlook.office365.com, SMTP port 587. Security level is STARTTLS, authentification OAuth2. These are the changed options requested by the company IT. The window popping up when trying to send a message asks me to chose a certificate for athentification and suggests "Adobe Conetent Certificate 10-7". Neither installing this manually, accepting, or changing something under "further options" changes the outcome that the message will be timed out. As my private e-mail also uses port 587, and it still works perfectly normal, this port is not generally blocked by the windows defender or antivirus (I use Kaspersky). Maybe someone has an idea what it happening here? Or knows if to slve it by installing a particular different certificate?