Email does not work

[md5]

As it currently stands, anything in Wordpress that needs to send email is broken. The wp_mail function that is used for sending out email by default is a thin wrapper over PHP's mail function, which defaults to calling /usr/sbin/sendmail -t -i (cf. http://php.net/manual/en/mail.configuration.php). There are php.ini settings for SMTP, but they are only used on Windows.

For my own work based on this image, I've been installing ssmtp and configuring it to use an external relay host for SMTP, but that's clearly not a turnkey solution for everyone. It also looks like there are many Wordpress plugins that provide SMTP support, but I don't think that installing any of them by default in this image seems reasonable.

Perhaps all of this should just be documented, but I wanted to get it on your radar.

[tianon]

Yeah... This was a hole we've had on our radar for a long time now, but
didn't have a good solution. Perhaps an actual issue will get some
brainshare going. We thought about something like ssmtp, but there really
is no good solution that'll work for 90% of users out of the box. Email
is hard. :(

[md5]

It looks like WP actually uses something called PHPMailer under the hood, which does support SMTP, but it requires a custom hook for configuration: http://codex.wordpress.org/Plugin_API/Action_Reference/phpmailer_init#Examples

[omarabid]

@md5 An alternative is to use a service like mailchimp and Mandrill. I know these are paying services, and not on your own service but the good thing (for Mandrill) is that you can opt out at any moment.

My experience is, your server emails will be probably put in SPAM folder. This is not the case for Mandrill.

[md5]

@omarabid using Mailchimp or Mandrill still requires using SMTP, which isn't supported out of the box by Wordpress under Linux. As I mentioned in an earlier comment, it would be possible to add one of the WP plugins that supports SMTP, but I don't think it would be reasonable for a generic Wordpress image to include specific plugins.

In my case, I was using ssmtp to connect to Google Apps with a dedicated mail user. This will avoid spam issues just as well as Mandrill. The case you're talking about is likely the default scenario of a PHP app using the local /usr/sbin/sendmail to send its mail out with no relay host settings. In that case, assuming the IP either isn't listed in the domain's SPF records or the IP is part of a spammy netblock, you will indeed have deliverability problems.

[omarabid]

using Mailchimp or Mandrill still requires using SMTP

No, otherwise, what's the point of using Mandrill.

[md5]

Ok, you're right that you can use Mandrill with their REST API instead of SMTP, but that requires installing this plugin or some other plugin that knows how to use that API.

As for the point of using Mandrill with SMTP, there are a ton of reasons you might want to do that, including open tracking, click tracking, deliverability concerns, email volume, etc. Not of those advantages of the Mandrill service rely on using the REST API.

[omarabid]

@md5 I was just suggesting a solution. Obviously, this should be available/fixed for the official Docker repo.

[booyaa]

Wondering how modular you can make the smtp solution> A nice implementation that I've seen is this one https://github.com/catatnight/docker-postfix , but it does bolt on TLS and and OpenDKIM. Perhaps it could be paired down to just postfix? I'm assuming it would only be used via container link so you don't need TLS. DKIM is fall back to avoid DNS shenanigans, admittedly not having it or SSP will probably cause some filters to flag you as spammy.

Thoughts? I think it's time to retreat to the lab 😀

[timwsuqld]

We are using SSMTP to relay to our main mailserver.
We have a php sendmail.ini file that contains the single line:

sendmail_path = /usr/sbin/ssmtp -t

We have a sed in the Dockerfile that changes the mailhub, rewritedomain and removes the hostname line from the ssmtp file (this way it gets the container id as the hostname)

RUN sed -i -e 's/mailhub=mail/mailhub=ourmailrelay.domain/' \
    -e 's/#rewriteDomain=/rewriteDomain=ourdomain/' \
    -e '/hostname=/d' \
    /etc/ssmtp/ssmtp.conf

This works really well, and as ssmtp isn't a daemon, it doesn't require any process management

[md5]

@booyaa I don't like that the Postfix container you mention is using supervisord and running its own rsyslog, but that's a moot point probably.

I think the real issue is that PHP is still going to expect a working sendmail-compatible command which will need to be configured to talk to the linked SMTP container (whether it's postfix or some other SMTP server). Getting such a setup working and maintaining it would be error prone.

I still think the best that can be done here without assuming too much is simply to document the options.

[booyaa]

Random musing: this problem would be a great candidate for a mail service docker-compose.yml firing up smtp, imap, spam assassin, clamav and webmail

[md5]

@booyaa 👍

[pierreozoux]

One good option is to configure SSMTP with ENV variables.
This way, you could put your GMAIL or Mandrill cred, and it would work out of the box!