It takes a long time to get pop3 email

hi, I’m trying to retrieve top 50 pop3 messages from a account , it is taking a long time , over 4 minutes. I change to another account, also get top 50, just takes several secs. Anyone can tell me why ? Is this related to the number of emails in the mailbox? one account have 300+ messages, run quickly, another have 1700+ ,run slowly.

Thanks and Best Regards