Thanks, I was just checking the update here: Auction House Issues - #23 by Bornakk “If a character buys commodities in high quantities, they may not be able to access their mail.”
Looks like it’s a known issue, so I’ll just be patient for now. Hopefully they figure it out soon 
EDIT: For anyone curious, my banker appears to be functioning again, currently slowly collecting the stupid amount of linen I bought from the mailbox, woo!