> So far no problems delivering to Gmail. I was initially junked by Outlook, but that fixed itself after a while since I had sent enough emails to build up reputation.

For me, Google has been really relaxed in terms of receiving mail from selfhosted services in the past. Stopped using gmail for monitoring stuff a few years ago, but up until then, every single cron job / monitoring mail was delivered into my gmail inbox. Outlook is another story. They may just throw your mail away without even a bounce. Had to deal with that several times at $PREVIOUS_JOB.