I have a REST service running inside my ISP where I can create/manage some accounts. Now I want to add email verification to ensure that i.e. sensitive data cannot be tampered by malicious persons even if they have hacked the password. One example is to avoid account hijacking by changing the email address of the user account.
However port 25 is absolutely blocked by the ISP with no hope of getting it lifted.
What are my options to send a verification email?
Can I use some other means of MFA that is as convenient as just sending an email with a temporary link? i.e. https://my.site.com/verification/?code=ece07f7c-7496-466f-8af4-792af68ba548