[BUG] Invalid email can be passed as argument for MAIL FROM, RCPT TO commands

[bestwebua]

New bug checklist

• I have updated smtpmock to the latest version
• I have read the Contribution Guidelines
• I have read the documentation
• I have searched for existing GitHub issues

Bug description

Regex for validation of email works in wrong way. We can pass to MAIL FROM, RCPT TO invalid email, like a@a.com@b.com. Seems when wrong email ends on valid domain it passes (a@a.com@b.com). We need to fix it and cover via tests.

Complete output when running smtpmock, including the stack trace and command used

INFO: 2022/11/18 19:20:12.419178 SMTP session started
INFO: 2022/11/18 19:20:12.419265 SMTP response: 220 Welcome
INFO: 2022/11/18 19:20:12.419533 SMTP request: EHLO gibson.biz
INFO: 2022/11/18 19:20:12.421156 SMTP response: 250 Received
INFO: 2022/11/18 19:20:12.421370 SMTP request: MAIL FROM:<evonne.langosh@hammes.ca>
INFO: 2022/11/18 19:20:12.421935 SMTP response: 250 Received
INFO: 2022/11/18 19:20:12.422099 SMTP request: RCPT TO:<a@a.com@b.com>
INFO: 2022/11/18 19:20:12.422823 SMTP response: 250 Received
INFO: 2022/11/18 19:20:12.422972 SMTP request: DATA