You need a DMARC policy, and then dkim or and spf record set up. Without these a lot of email providers will just assume your emails are spam.

No, although I don’t host my own email so my “reputation” is bound to my email provider (soverin.net). I’ve found https://mxtoolbox.com/SuperTool.aspx to be useful when checking email sending at work, though

Set your DMARC and SPF

https://kb.mailbox.org/en/private/custom-domains/spf-dkim-and-dmarc/

Depending on how the hosting provider sets things up, you might have to create a few dns entries (spf, dkim, dmarc) to help your reputation. Also avoid using addresses historically reserved for admin stuff, like admin, mail, etc.

I've hosted websites since 1997, and for the last decade, I've given up fighting just that. I use - and this is not an ad, but is an endorsement - mxroute to handle that. They handle fighting blacklists so I don't have to worry about it.

Glad to explain more if wanted, but it's pretty simple to set up - as long as you control your DNS.

Besides the DMARC, SPF and DKIM stuff, try to get your domain from a hoster that will try to keep you off large spam lists. Spamhaus is a popular one of those lists.

I recently swapped to a custom domain with PurelyMail as the backing and sometimes it doesn't even go to spam but straight to the void. I had to add it to my work Outlook's trusted list for it to even show up at all. Also signing up for store rewards the other day the system wouldn't even recognise my address as valid. That said, all my emails to businesses have been responded to as normal so I have yet to have major issues.

You can run email on a custom domain, but as other replies demonstrate, it's a huge challenge these days. (My primary email is on a custom domain, but I probably wouldn't do it again if I hadn't already been on it for two decades.)

Almost everyone does.

As long as your DKIM and SPF are correctly configured in your DNS (usually your registrar) and the IP of the email server is not blacklisted by some others, you should be just fine.

It's available. If I wasn't in bed already I'd buy that domain and put up a website to taunt you with.

A domain? No. You'll have to pay for your domain as long as you want to keep it. They're not very expensive though. A basic .com will usually run you about 10–15 dollars per year.

Yes, but you'll have to use an alternative DNS system that very few people use.

In that case, something like njal.la is probably your best bet.

Downside with Cloudflare email routing is one way only

You can add an SMTP https://www.youtube.com/watch?v=nNGcvz1Sc_8.

Oh no, the difficulty.

Or would you prefer to argue with Gmail after they delete you Gmail account for reasons?