Takes very long time to delete msgs from Spam

I typically get hundreds of spam messages a day. They collect very nicely in my SS spam folder. But they they add up and I want to highlight and delete them into the trash icon. I can easily highlight, say, 20 or so and high the trash can and it says “preparing to delete” for a few seconds and then poof they are gone. I would LIKE to highlight 500-1500 at a time but when I do,the message “preparing to delete” can sit there for three minutes and more before anything happens.
I am on Mac Mojave and the latest SpamSieve, the one that just came out. Is this normal? I remember this behavior from Sierra and past SpamSieve versions but in the last version I had been using this was fixed and I could highlight and get rid of hundreds of things at once. But now I am not sure if this “immediate delete” ever worked under Mojave. Perhaps it just worked under Sierra?Thoughts?

Are you referring to Apple Mail or another mail client? In any case, this would not be affected by SpamSieve because the mail storage and deletion is fully handled by the mail client.

Yes Apple Mail
Thanks, must be something else then.