[erksa]

For any critical email delivery make sure you can address this thing with the mailsender of choise:

1)SPF,

2)DKIM,

3)DMARC [2] (DMARC is often forgotten or can be super noisy when set up. Postmarc offers a aggregation service for free that sends you a weekly summary),

4)Dedicated IP

5)Reverse IP look up [1] (locate a dns PTR record for that IP address) should match the sender.

Not everyone supports 5).

4 and 5 is what you end up paying for, but totally worth it. Sendgrid, SES, Mailgun etc.

[1] https://www.mailgun.com/blog/deliverability/reverse-dns-whit...

[2] https://dmarc.postmarkapp.com/

[joshstrange]

And 1 surprising thing (to me) is some places (iCloud was what bit me) alway want you to be able to receive email (have MX records). Even though I have no need to support incoming emails iCloud was blocking my sending until I got that setup. The incoming emails just go to a black hole but that's enough.