You can get your own protonmail account for free (here) to ensure encryption is full and end-to-end, including for attachments.
If you send me documents or tips, and prefer to do so anonymously, you can suggest the names of the people I can contact to verify the information.
I don't recommend using corporate connectivity (your work phone, for example) to contact me if you're worried about your employer knowing that we've spoken, unless you're using methods that support end-to-end encryption, like ProtonMail or the apps below.
Even then, while the content of our messages may be visible only to me and you, it may still be possible to see who you've contacted and when. That's less the case for apps and contact methods that use random usernames, like Threema. Use your best judgment.
Safest and easiest option. You don't need to use your email address or phone number to message me.
You don't need to use your email or phone number to contact me. Note my username is donatopmancini.