Set PTR
PTR or reverse DNS or rDNS tell the domain name of your IP, you may set this record in your VPS console like this
or if it is not supported by your ISP just submmit a ticket to apply it.
DNS Records
| type | record | value | ttl |
|---|---|---|---|
| A | @ | 130.255.76.237 | 600 |
| A | 130.255.76.237 | 600 | |
| A | www | 130.255.76.237 | 600 |
| cname | smtp | 130.255.76.237 | 600 |
| cname | pop | 130.255.76.237 | 600 |
| cname | imap | 130.255.76.237 | 600 |
| mx | @ | mail.dba.pw | 600 |
| text | @ | “v=spf1 mx ~all” | 600 |
| text | _dmarc.dba.pw | “v=DMARC1; p=none; rua=mailto:dmarc-reports@dba.pw” | 600 |
| text | s20190305648._domainkey.dba.pw | “xxxx” | 600 |
start poste.io docker
docker run \
-p 25:25 \
-p 80:80 \
-p 110:110 \
-p 143:143 \
-p 443:443 \
-p 587:587 \
-p 993:993 \
-p 995:995 \
-v /etc/localtime:/etc/localtime:ro \
-v /var/maildata:/data \
--name "mail" \
-h "mail.dba.pw" \
-t analogic/poste.io
Get certificates from “Let’s encrypt”
Loin to admin panel via like https://mail.dba.pw go to like https://mail.dba.pw/admin/le/ 
Webmail
https://mail.dba.pw/webmail

Admin panel
https://mail.dba.pw/admin/login

client
pop
Note: Use POP protocol will keep all mails in local machine and delete from server side. server: pop.dba.pw:110 username: line@dba.pw connection security: starttls 
imap
server: imap.dba.pw:143 username: line@dba.pw 
smtp
serve: smtp.dba.pw:587 username: line@dba.pw connection security: startttls 
Refer
refer1: https://qing.su/article/139.html refer2: https://poste.io/doc/client-settings
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