Don't use email to send your passwords to anyone, no matter how much you trust them.
It's not about trust and it's not about them. It's about who can see the email as it moves electronically from your mailbox to theirs. Imagine sending a hand-written letter in a clear plastic envelope. The mailman or anyone at the post-office could read it.
This applies to passwords, credit card, bank account and social security numbers as well. Don't send any private information using email, unless you know for sure that you're using a special secure email system, or a secure service lke sendsafely.com
And if a company ever sends your password to you via email, question them on this practice and ask them not to. It can be a sign of poor security and information management. All secure systems store passwords using unreversible encryption methods, which means no one (including their staff) can ever see or retrieve your password. For more information, see here: Retrieving Passwords
If you absolutely must send your username and/or password to someone electronically, use a text message and send them separately. Send your username via email and send the password as a text message. Keeping them separate reduces the risk of someone else seeing those two pieces of information together.