from United States
If you are trying to send Emails to this domain,
this is how to avoid rejection:
- Use a reputable Email service that:
- employs free software1;
- is configured to Internet standards, including SPF and DKIM;
- has encryption and authentication configured;
- uses reputable IP ranges;
- is whitelisted by dnswl.org; and
- that will not provide/sell/leak2 your information to anyone else without your consent.
- Send text Emails from addresses that will accept replies.
- Do not attach files to your Emails, send links to secure storage instead.
- Ensure you don't include any information in an unencrypted
Email that you don't want to share with the general public.
- Seek professional technical support to get the systems you use to send Emails
configured correctly, and to sign and encrypt your Emails with valid GPG keys.
- Do not use phishing phrases, and spam trigger or curse words, e.g.,
s**, girl/boyfriend, payment, lottery, investment, heritage, pills, pharmacy, weight loss, make money,
act now, last reminder, Microsoft/Google/Amazon-Support, out-of-context wording ... you get it.
- If you have a website with the same domain as the Email address you are using,
ensure the domain gets high reputation scores, e.g., from postmaster.google.com.
- Ensure any parts of your Email address are never, ever used to send unsolicited or bulk Emails, or to spread malware.
- Check your Email score, e.g., by using mail-tester.
If you followed the points above and
your Email is still getting rejected,
we can't help you because proper sending is your responsibility3.
 Is a device truly secure if you have no idea what it is doing?
 In most cases this means you will have to use a paid-for Email service.
 According to RFC5321 chapter 2.1, "The responsibility of an SMTP client is to transfer mail messages to one or more SMTP servers, or report its failure to do so.", confirmed by the Bundesgerichtshof.
The Internet ends here.