Is this a problem with my css changes to the plugin

Try temporarily disabling these changes, clean the caches and check again.

Any ideas?

It may be caused by your mobile browser or mail client.

You can add your own custom styles for links.

In start.php or Bootstrap class:

elgg_extend_view('css/html_email_handler/notification', 'my_plugin/styles.css', 1000);

In my_plugin/styles.css:

a, a:hover {
  color: #333 !important;
}

You can use this skeleton plugin (Elgg 3).

Learn more.

Thank you. I'll see if that helps.

Thank you Nikolai Shcherbin but that didn't seem to help. On the mobile device it is actually leaving off: 

file:"
<br>
<a 

From the string and tag "View and comment on the file" <br><a rel.... It then inserts the full URL in quotes and puts this after it:

rel="nofollow"

Then leaves off:

noopener noreferrer" target="_blank"

And the URL, but picks up with:

style="text-decoration:none;color:#4682B4;">

And then writes out the URL as a link but doesn't show the ending </a> tag.

I am definitely a newbie, but this seems like some error in the php that puts together the notification code for emails about file uploads. It doesn't do it on other notifications. It's very strange. I looked at some emails that were sent out before I tweaked the CSS and it did the same thing. That seems to be a problem with either plugins or core files. 

As a side note, these emails all take much longer to go through than any others.

As a side note, these emails all take much longer to go through than any others.

As a side note, these emails all take much longer to go through than any others.

That seems to be a problem with either plugins or core files. 

I don't think Elgg core is the reason of this issue because Html email handler plugin works fine on all our sites (Elgg 3.3.23).

(By the way, I highly recommend to upgrade your app to the latest Elgg version).

Try to disable all 3rd party activated plugins except Html email handler plugin, clean the caches and check out an issue again.

Enable these 3rd party plugins one-by-one to find the problem plugin.

Another question is where did you download this plugin?

I'll try that. Thanks.

I think I got it from Jerome Baker's page for the plugin. I'll reload it and try again. Thanks.

I think I got it from Jerome Baker's page for the plugin

This is the correct link if you mean this https://elgg.org/plugins/709492