I want to send emails from my work computers so that I can notify myself when various long-running tasks are completed. As I understand it, the command below looks up bar.com's MX record, makes a connection to the mail server and does SMTP to send the message:
echo “Hello world” | mail -s “Hello world” [email protected]
What do I need to know so that I can avoid being flagged/blocked as a spammer?
There is no difference between sending mail via the mail command or via any other program. As such a mail send via mail (1) is not more nor less likely to be identified as spam.
( I would add that this is the default way in which many non-cron tasks send you their mail, but I have no evidence to back that up. )
As to avoid having your mail seen as spam: Make sure that your mail does not look like spam. E.g. not just a single HTML link, not just a picture. No l33t spelling. Valid origins. Etc etc. Non of these are specific to the mail command.
mailto be different than sending with anything else? (And what does this have to do with Unix or Linux?)mailrelies on some other software in order to send beyond the box, so don't assume this will work at all until you try it.