Indicates the list contains credentials specifically for logging into email accounts (IMAP/POP3/SMTP).
Often used by leakers to claim the credentials are valid, fresh, or have a high "hit rate" for successful logins. HQ #6MAIL ACCESS& EDU Access D90K #6DDARK .txt
Likely refers to the quantity of entries in the file, in this case, 90,000 lines of data. in this case
Often a signature or branding for the specific group or individual who compiled and shared the data. Security Implications HQ #6MAIL ACCESS& EDU Access D90K #6DDARK .txt
Immediately update passwords for sensitive accounts, especially those that share a password with the leaked email address.