Bug 1934201

Description of problem:

The ovirt-engine-notifier fails to send emails unless MAIL_FROM is set in 90-email-notify.conf. This only seems to happen for me on a recent 4.4.4.7 installation - an older 4.3.7.2 installation successfully sends email even if MAIL_FROM is undefined.

In the /var/log/ovirt-engine/notifier/notifier.log I would see entries like this:

2021-03-02 12:45:46,841Z INFO    [org.ovirt.engine.core.notifier.transport.smtp.Smtp idle] Sending e-mail subject='alertMessage (ovirt-engine), [Migration started (VM: vm-ataylor, Source: vm-host-1, Destination: vm-host-2, User: ataylor@internal-authz). ]' to='user'

but I would never see an entry confirming the email had been successfully sent. MAIL_SERVER and MAIL_PORT were both set correctly (tested by connecting to that server/port via telnet on the oVirt Engine). The logs on the mail server and a tcpdump on port 25 showed nothing even attempting to connect.

After enabling debug mode in ovirt-engine-notifier and connecting an IDE to it, I found it was hitting a null pointer exception here:

https://github.com/oVirt/ovirt-engine/blob/ovirt-engine-4.4.4.7/backend/manager/tools/src/main/java/org/ovirt/engine/core/notifier/transport/smtp/Smtp.java#L211

As soon as I set MAIL_FROM and restarted ovirt-engine-notifier emails were sent successfully.

Version-Release number of selected component (if applicable):

4.4.4.7

How reproducible:

Always until MAIL_FROM is set.

Steps to Reproduce:

1. Follow the RHEV 4.4 documentation to configure event notifications and set up the notifier service:
https://access.redhat.com/documentation/en-us/red_hat_virtualization/4.4/html/administration_guide/chap-event_notifications
2. Leave MAIL_FROM in 90-email-notify.conf as the default value (empty)
3. Trigger an event in oVirt which leads to a notification being sent.

Actual results:

The email notification is never sent.

Expected results:

An email notification is sent. Perhaps MAIL_FROM should be marked as a required value, but ovirt-engine-notifier seems to work without it being set in 4.3.x.

Additional info:

I don't know Java, but having done a bit of reading of the MimeMessage.setFrom documentation I thought this might have something to do with setFrom attempting to generate a from address from the local hostname. In case it was related I checked the oVirt Engine hostname/DNS configuration and it all seems fine, but perhaps there is an environmental issue.