I configured it once last year without success. I didn't expect that configuring a free mail server would be so complicated. A few days ago, I happened to see someone made a dock image on GIT, packaged the various programs of the mail server, and matched them up, and then the idea of configuring the mail server was triggered again, because the docker deployment was used on the vps. application, so the use environment is ready-made, pull down the docker image, the operation is very simple, but still need to configure a lot of things, stopped for a while in the middle, browse the products of various mailbox providers, I found that the mailbox service is better than renting one VPS hosting is much more expensive. Insist on the successful configuration of the mail server.
According to the instructions on git, after the configuration is completed, the first problem is that the mailbox cannot be created on foxmail. The log prompts that the authentication password is inconsistent. After repeated trials, delete the mailbox and create the mailbox, it is unsuccessful. Look at the submission on git. issue, add: restart: always,SSL_TYPE=letsencrypt in docker-compose.yml, restart docker, because linode vps host is mainly ipv6 address, and remove ipv6, operate linode settings, do not let linoe create network configuration, I don't know if this step starts It works, and the operation has changed anyway, and finally a mailbox can be created in fomailh.
The second problem is that I can't receive mail, and it says that the domain name cannot be found. I reconfigure the domain name on the dns server. The name of the A record used in the original mx record is now changed to the full domain name of mail, and the mail is received successfully.