Outlook Version 16.114.1 (26102031) not *sending* mail-BT is my mail service provider

BT webmail working shows that sending is possible through BT’s website, but it does not prove Outlook’s outgoing-mail connection is healthy. Because both Legacy and New Outlook can fail, there is not enough evidence to call this a confirmed Outlook–BT conflict. During the next failure, capture the exact send error and time, and test a short message without attachments. Confirm Outlook is not working offline. In the account settings, compare the outgoing server, authentication, port, and encryption with BT’s current requirements; Microsoft specifically identifies SMTP authentication and incorrect settings as possible causes. Test the same account on another trusted network to help distinguish a network-specific restriction. Keep webmail as a temporary sending option. Give Microsoft support the build, error, timestamp, and cross-client results, and ask BT to check the corresponding SMTP connection. Avoid deleting the account before protecting any locally stored mail.