This means the email will come from Twitter with "
You can see it in the link below in the screenshot version (next to Favorite) - not sure if it will show up in the embedded version though.
The Queen does the washing up once a year, after the summer barbeque at Balmoral. She retires to a special hut to do it. (@walkthelinesldn)
— The QI Elves (@qikipedia) December 21, 2012
I can imagine this either being really great, or being really annoying and quite puzzling to people who aren't currently using Twitter and who might therefore be a bit surprised to get messages from Twitter. The subject will look like this "Jo Brodie (@JoBrodie) shared a Tweet with you!" - so it will come from whatever account is logged in, so if you don't know their Twitter handle then it might be confusing.
If you're not interested in receiving these tweetly emails you can pre-emptively block them by setting a filter (for all of your email accounts) that deletes any email coming from @postmaster.twitter.com or where the subject contains the phrase "shared a tweet with you". People who try and send you tweets will get a message saying " ".
If you don't want set up filters but emails start to come in (OK I'm not really imagining a deluge) you can still unsubscribe from future messages by clicking on the link in the text at the bottom of the email.
I've got several Twitter accounts and several email addresses (one for each) and when Twitter started emailing everyone to tell us what was happening on Twitter (I mean... seriously?) that was pretty irritating having to manually unsubscribe from each one to stop receiving the spam emails.
On the plus side it's another way to 'trap' a tweet, but it only works for individual tweets. If you want to grab someone else's (or your own) timeline I'd recommend Twilert which sends an email every day. Mind you, Twitter's also rolling out the opportunity to download your entire Twitter archive too, but only your own I think.
Further posts in the Twitter tips series...