Sometimes POP. I recently saw SM login take 30s when POP took 15s. Right now (2045 msgs, 49Mb) SM has no appreciable delay and POP likewise. But I'll check more in future and let you know.
I don't. Only rarely is there a POP3 delay. I've never seen POP take more than 15s. Whereas SM is sometimes taking over a minute.
It needs only 25 to fill the initial message list. It is bonkers to download /all/ of the message headers, as Support confirms it does:
No wonder "Dreamhost doesn't recommend using Squirrelmail as your main email client because it taxes the servers" ! DH's removal of quarantine from IMAP (Razor) to SquirrelMail (JF) has surely increased the number of SM logins greatly. It seems to me this would be good to fix for the benefit of all IMAP users as well as Quarantine readers. And surely the appropriate fix is to get Quarantine back out of SquirrelMail, ratehr than try to fix the SM itself, never designed for that.