First disable pipelining under Settings>>Email Accounts, click your account, click Incoming>>Advanced, and uncheck both, PIPELINING options.
If no better, Settings>>Email Accounts, click your account, click Incoming>>Advanced, and tick,
"Use RETR instead of TOP"
If still no good, can you please try deleting the problem email account and re-importing it.
Please open Mailwasher Pro and click, Settings>>Accounts, click your account and click, "Remove Account", click, "Yes, remove it", close and restart Mailwasher Pro.
In Mailwasher Pro click, Settings>>Accounts "Import Account" and follow the directions.
If there are no accounts listed, cancel to exit this screen and click, Add Account, choose your account type and add account manually.
Full directions are available for this from here:
Mailwasher Pro >> Help >> Help Topics >> Settings Screen >> Accounts