Nextcloud, Qbittorrent, Truenas and loads of other svcs take optional email credentials for sending alerts and other features (eg. password recovery for nextcloud).
What email providers do people usually use to make this process simple to set up? For example, Microsoft doesn’t allow basic auth anymore so it’s supposedly not possible to use via most of these setups, and some other services seem like they have a low inbox size (does this matter?)
I do this with my home network using FastMail. You can create App specific passwords for each service you add email notification support for. This means you don’t risk compromising your full accounts passwords. You can also put constraints on each app password, such as limiting it only to sending emails but not reading email or looking at your contacts and files. This is nice in case any of my passwords are leaked.