Voicemail to Email - Always 'Failed' Status

In FusionPBX Extension I have set 'Voicemail Mail to ' a proper email ID for my extension. Also in Advanced ->Default settings, Email settings are configured as per the document with port and everything.

So when I call my extension and leave a voicemail, I see that voicemail gets saved, I can play and hear it. I go to Status->Emails, I see the voicemail with status 'Failed'. I tried re-sending but the email not coming through.
In Log viewer I do see

2018-01-30 16:17:46.786576 [DEBUG] switch_utils.c:1180 Emailed file [/tmp/mail.15173290647ad0] to [myEmail@hotmail.com]

Could you please point me what I am missing??

Thank you!
I am still having a similar issue. The only difference on mine is that if I click resend it goes right through so it doesn't seem to be a setting issue on my email. It just fails on the first attempt for the emails. It has been a big pain as I have to go in daily and check for failed emails and click resend on each.
I checked what I was able to figure out how to check. I was hoping for some assistance to try to figure out how to check/enable more detailed logging.

I had started a different forum post directly relating to my issue back in the end of January but never got a response on it. Been following this one as well in hopes of it being a similar issue.

The error that I was able to see is:

SMTP -> ERROR: Failed to connect to server: (0)
The following From address failed: admin@mydomain.com
Mailer Error: The following From address failed: admin@mydomain.com

But as soon as I click resend in FusionPBX it goes right through, so it doesn't really make much since to me.
Sorry know this post is a bit old. I'm experiencing the same problem.

The only thing is that when I leave a voicemail message it doesn't even appear under pending messages on email anymore. If I resend anything that failed it delivers without a problem.

Has someone managed to get a solution for this problem?

Thanks a stack
@Incubugs, Thanks for your reply.

I'm actually making use of our own smarthost to relay email (ISP). Now the problem is that when I actually leave a voicemail, with email as an attachment, it doesn't even show an attempt to send the mails. If I tail /var/log/exim4/mainlog it doesn't show up there, showing that no attempt was made to send an email. I've confirmed that the settings are correct. It basically looks like fusion isn't making an attempt to send the email nor queue it under status > emails.

Not sure what else to really check :(
Just to add. I'm seeing the below error:

2018-06-29 07:01:29.951911 [ERR] mod_lua.cpp:203 ...scripts/app/voicemail/resources/functions/send_email.lua:166: attempt to index global 'subject' (a nil value)
stack traceback:
...scripts/app/voicemail/resources/functions/send_email.lua:166: in function 'send_email'
/usr/share/freeswitch/scripts/app/voicemail/index.lua:588: in main chunk
/usr/share/freeswitch/scripts/app.lua:48: in main chunk

Not sure if this is the actual problem?
The way we did the upgrade was:
1) Install new 4.4 MB on new servers
2) Migrate 4.2 MB DB over and make the necessary corrections to accommodate 4.4 settings.

The guys from Fusionpbx did the upgrade for me really so I would assume that it was done correctly. We never tested voicemail delivery though.