Robert, we are all confused i think. The 90 seconds delay the OP is talking is about what happens IN wpForo. What happens AFTER the emails are queued ...

Again, do not guess, use the debuger to see what exactly is taking your php and db time. And 17 emails (as you say above) should NOT take a few secon...

Then with the debuger you can find where the delay happens. You can pinpoint the problem.

@robert He is not talking about GD mail queue, i think he is talking about wpForo. As for GD mail queue, works just fine with wpForo.  

For how many subscribers we are talking about ? 90 seconds is way too much. For how is the big forum ? Are you sure that the delay comes from wpForo...

If you want and can, deactivate the smtp post plugin and install GD mail queue. Enable the option to process ALL email and tune the queue to send ever...

That make some sense, but even so it is a hosting problem. A slow "way" to send emails. Smtp sends directly the emails or routes them to a mail server...

Well wpForo has not any kind of maintenance like that, i mean to cleanup/delete anything. Posts or attachments. So i think your problem doesn't come f...

In most cases it is hosting related.

There is no Pro/Paid version of wpForo. Just some paid plugins for people that need them. There is nothing hidden in this, wpForo plugin is completely...

Install and use Postman plugin. And see if they still mark them as spam.

Also this is the most optimized forum, talking about SEO and everything. Well respected. An example: This url href="https://www.warriorforum.com/sear...

Well i created a PAGE with that title as here (for test) and my SEO plugin (SEO Framework) reported also long and will be truncated. But the truncated...

Can you show us HERE on this forum an example ?