Postfix SMTP relay docker image. Useful for sending email without using an external SMTP server.
Default configuration is an open relay that relies on docker networking for protection. So be careful to not expose it publicly.
docker pull mwader/postfix-relay or clone/build it yourself.
All postfix configuration options
can be set using POSTFIX_<name> environment
variables. See Dockerfile for default configuration. You probably
want to set POSTFIX_myhostname (the FQDN used by 220/HELO).
Note that POSTFIX_myhostname will change the postfix option
myhostname.
docker run -e POSTFIX_myhostname=smtp.domain.tld mwader/postfix-relay
app:
# use hostname "smtp" as SMTP server
smtp:
image: mwader/postfix-relay
restart: always
environment:
- POSTFIX_myhostname=smtp.domain.tld
- OPENDKIM_DOMAINS=smtp.domain.tld
When sending email using your own SMTP server it is probably a good idea to setup SPF for the domain you're sending from.
To enable DKIM,
specify a whitespace-separated list of domains in the environment variable
OPENDKIM_DOMAINS. The default DKIM selector is "mail", but can be changed to
"<selector>" using the syntax OPENDKIM_DOMAINS=<domain>=<selector>.
At container start, RSA key pairs will be generated for each domain unless the
file /etc/opendkim/keys/<domain>/<selector>.private exists. If you want the
keys to persist indefinitely, make sure to mount a volume for
/etc/opendkim/keys, otherwise they will be destroyed when the container is
removed.
DNS records to configure can be found in the container log or by running docker exec <container> sh -c 'cat /etc/opendkim/keys/*/*.txt you should see something like this:
$ docker exec 7996454b5fca sh -c 'cat /etc/opendkim/keys/*/*.txt'
mail._domainkey.smtp.domain.tld. IN TXT ( "v=DKIM1; h=sha256; k=rsa; "
"p=MIIBIjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEA0Dx7wLGPFVaxVQ4TGym/eF89aQ8oMxS9v5BCc26Hij91t2Ci8Fl12DHNVqZoIPGm+9tTIoDVDFEFrlPhMOZl8i4jU9pcFjjaIISaV2+qTa8uV1j3MyByogG8pu4o5Ill7zaySYFsYB++cHJ9pjbFSC42dddCYMfuVgrBsLNrvEi3dLDMjJF5l92Uu8YeswFe26PuHX3Avr261n"
"j5joTnYwat4387VEUyGUnZ0aZxCERi+ndXv2/wMJ0tizq+a9+EgqIb+7lkUc2XciQPNuTujM25GhrQBEKznvHyPA6fHsFheymOuB763QpkmnQQLCxyLygAY9mE/5RY+5Q6J9oDOQIDAQAB" ) ; ----- DKIM key mail for smtp.domain.tldpostfix-relay is licensed under the MIT license. See LICENSE for the full license text.