Hello, I have two Hotmail accounts on Thunderbird, one @hotmail.com and one @hotmail.es (if that makes any difference). Both working fine since switching from Windows to Linux a week ago. As of this morning, the hotmail.com address can't send emails (it can receive them no problem). The hotmail.es email can send and receive no problem, although it has the same settings. When I try to send an email I get the error: "login to server smtp-mail.outlook.com with username ...,@hotmail.com failed. " If I click on 'enter new password', it just tries to send the email again without asking for a password, although I don't think that's the issue because I can login via the outlook.com website using that same password. When I click cancel, I get the error: "Sending of the message failed. Unable to authenticate to outgoing server (SMTP). Please check the password and verify the authentication method in account settings/outgoing server/(SMTP)". I've checked both POP settings and outgoing server settings and they are the same for both accounts, apart from the email address obviously (pic below). I got these settings from the Microsoft page: https://support.microsoft.com/en-us/office/pop-imap-and-smtp-settings-for-outlook-com-d088b986-291d-42b8-9564-9c414e2aa040 Microsoft support said it's a Thunderbird problem. I've tried disabling my firewall and VPN. Would appreciate any other ideas (in absolute beginner terms if possible). Many thanks for reading. Thunderbird 128.0.1esr (64-bit), Linux Mint 22 Cinnamon 64-bit, Gufw Firewall 24.04.0, VPN Surfshark 3.0.3, Hotmail.com, ISP = Three 5G