Is it safe to send passwords over email?
Not as plain text. An email is stored on your mail server, the recipient's, every backup of both, and every device either of you signs in from. It is searchable for years and forwards with one click. Transport encryption between servers protects the message in flight, not at rest in a dozen mailboxes.
Gmail and Outlook both offer extra protection. Gmail's confidential mode can set an expiry and block forwarding, and Google Workspace customers can use S/MIME. Outlook can encrypt a message with Microsoft 365 Message Encryption or S/MIME. These help, with two limits: the password still sits in the recipient's mailbox for as long as the message does, and the recipient often needs the same provider or a certificate for it to work.