Why I'm not receiving an E-Mail when someone comments on my discussions even with "Notify me when people comment on my discussions." checked?

Why is it that the missing messages imported from the accounts.ini file disappear after a few seconds. When selecting the accounts.ini file from a mail folder, the missing messages appear for a few seconds, then they disappear so is there a way to prevent them from disappearing after import?

How do I transfer E-Mails to imap.mail.yahoo.com without a Content-Length header using IMAP when the E-Mails did not have a Content-Length header in the first place? 2 headers that Yahoo! mail adds for incoming E-Mails are X-Apparently-To and Content-Length header? The E-Mails are able to be transferred to Yahoo! mail without the X-Apparently-To header but the Content-Length header still shows up as a header on the E-Mails even though the E-Mails did not have a Content-Length header in the first place. The Content-Length headers prevents the E-Mail from being original during transfer to Yahoo! mail also it changes the MD5 hash of the E-Mails which people don't want because the Content-Length headers modify the E-Mails. How do I prevent this annoying header from appearing on E-Mails that are transferred to Yahoo! mail using IMAP.