One of poste.io best features is that it helps you to setup DNS in best possible way to avoid getting emails delivered to SPAM folder.
All values are suggested, not required and might not be best for your configuration but in majority of use cases should work as intended.
Log to administration: Server status → DNS diagnostics
First thing you need to know is what domain you will be using for your email server. I strongly recommend mail.your-domain.com since it looks like proper name for email server not something like ip-87-45.isp.com, which will highly probably end up in spam folder. Probably you will not have ability to change PTR record (known as reverse DNS) by yourself, so contact your server provider to change PTR record of your server IP address to mail.your-domain.com.
A and CNAME records
mail.your-domain.com A → 184.108.40.206 (your ip)
for some clients you can optionaly setup:
- smtp.your-domain.com CNAME mail.your-domain.com
- pop.your-domain.com CNAME mail.your-domain.com
- imap.your-domain.com CNAME mail.your-domain.com
Now if you refresh DNS diagnostics page all checks should be green. Still poste.io will not be able to receive and properly send emails - we need to setup delivery domain as well.
After email server installation default domain will be installed. Go to Virtual domains → your-domain.com [Show]
MX for your domain
your-domain.com MX mail.your-domain.com
Clicking on [create new key] will instantly generate new key dedicated for your domain. All emails send through will now be signed with DKIM key.
DNS DKIM, SPF, DMARC...
Click on [DNS diagnostics]:
your-domain.com. IN TXT "v=spf1 mx ~all"
This literary means to pass all emails from domain mail server and soft-fail from others. Explanation of options can be found at https://poste.io/spf?gmail.com
DKIM record (this is example only, copy one from your administration!):
_s20160910378._domainkey.your-domain.com IN TXT "k=rsa;p=MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA0FvkMuwN46vvtQCC1JZz7XzRE+l+Lf8/5XUKwWJXOcE7dJoZBbOE0Gz85phZ2q+y4l8D7t/hXDz9q+6/KVQDgJ9muaxSM/uS+KG0ds0QLEiV0GYCVu+ZZQSNPBPjOwlDvo3LraW00lMpd5dUj+xpr07ShfIoULhi7/7t76n5GZMse9yBa4hIhxSG/wCAB4D6IWYBURz9Pc75IDPDTlImr3TP/82YrsULY70CHaPHA1+j1VPA5lE+tnmeqxJW6P537xSutDppv8BZg4nlF3ojg2k6LB/cq15C4QRPAMs77pRA4GVnys1LEJ3JDvV3/csOCZ49oC4m44/TnWXk057OAwIDAQAB"
Public part of DKIM. You need to set selector (subdomain part) and TXT record exactly the same or it will not work.
_dmarc.our-domain.com. IN TXT "v=DMARC1; p=none; rua=mailto:email@example.com"
DMARC is not required but its very helpful method for recognizing delivery issues. Explanation of DMARC options can be found at https://poste.io/dmarc?gmail.com
autoconfig records are not required but helps some clients to do initial config
Now if all your checks are green mail server is ready to receive and delivery your emails! Now go and create your personal mailbox.