Thunderbird Can't Send Email

[MightierPen]

There is other older threads about this but I don't want to necro them.

My Thunderbird can't send email.  It receives email fine.  The internet says it could be antivirus.

This "trusted" thing is confusing.  Of course I don't trust any web address but I need it to work.
I'm not sure what is meant by "trusted".  Will Kaspersky just ignore it?  How can I make it not block the connection but also make sure nothing shady is happening?

I have gmail, proton and outlook accounts in Thunderbird.  Their "domains" all look very common to me, so if I "trust their address" isn't that a major vulnerability?  (Especially outlook, which looks to be a very common outgoing port.)  And is it trusting both outgoing and incoming traffic?  (Outgoing is a lot more likely to be safe than incoming).

I'm also confused as to adding to the exclusion: "A list of websites".  This is the same thing as an SMTP outgoing port?

Anytime I try to send email Thunderbird just sits there not working or else "The SMTP has failed" and I can't send email.  I have no idea what to do.