Would MTAs please stop sending hi-bit7 messages to other MTAs which do not advertise 8BITMIME! Recode it to QP or BASE64, damnit! The receiving MTA is entitled to strip the set bit7, which kinda makes things hard to read (while I know how to deal with blvde Stra_e, the advent of UTF-8 makes that blC6de StraC?e, introduces C0 control characters and makes typographic quotation marks into NUL-containing octet sequences (as their UTF-8 representation contains 0x80 octets) which let every sensible MDA terminate the line there). I even filed in the Debian BTS against the BTS (might be Drexim's fault, though).
Would MUAs please default to Quoted-Printable!
And mail hosters should use the same server when retrying delivery, to benefit greylisting. Or at least publish a list of outgoing IPv4 addresses they use for sending. Or use IPv6. Oh, and STARTTLS, while we are on my wishlist.
It's a sad day when the percentage of correctly encoded eMail messages in my INBOX is smaller than that of my Spambox...