Hi all, Roughly two weeks ago I lost the ability to send e-mails through Thunderbird for both my Hotmail account and my work account which is also Outlook based. All incoming messages are fine and my accounts sync non-outgoing messages just fine (in fact, my typical way of sending e-mails is to save to drafts and then pull up the draft in Outlook and send it). I know that this has been a problem for multiple users over the years and I've tried all the typical solutions. I'm currently using: outlook.office365.com Port 587 Starttls Oauth2 Although I have tried the workarounds that I've found in the discussion boards including: - alternative ports -SSL/TLS instead - no authentication (this worked for a similar problem many years ago) To me, the most glaring detail is that as soon as I'm off campus, it returns to working immediately which would suggest that the work network is doing the blocking. I've talked with our T&I multiple times and they confirm that nothing that they no of is blocking my SMTP which means its probably a setting they don't know about. They can also log into the e-mail settings and confirm that my SMTP is specifically not blocked (which makes sense because it works off campus). For context, we use Crowdstrike as our endpoint protection. We are a small place and my IT group is being pretty cool by throwing some time and resources at this. However, since none of them have any experience with Thunderbird, it would be great to give them a list of things to try. Thanks!