tilde.institute doesn't support POP or IMAP at the moment, so we'll need to use a little bit of a roundabout way of connecting to our mail address remotely. All you will need for this guide is sshfs, ssh itself, and an e-mail client that supports Maildir.
To send mail, all you need to do is run this command:
ssh -nNTL 25:localhost:25 yourusername@tilde.institute
And then set your SMTP server in your mail client to localhost and use port 25. You will now be able to send mail.
First, you need to mount your remote Maildir folder using sshfs. You can use this command to do that:
sshfs -v -o reconnect -o ssh_command="ssh -i ~/.ssh/id_yourkey" yourusername@tilde.institute:/home/yourusername/Maildir ~/Maildir
Then set up your mail client like you would with any other Maildir and point it to your mounted Maildir folder.