I would not recommend custom domain:
- It will decrease your privacy and anonymity (this domain is not used by anyone else in internet (AKA not public domain), this means that every service will know that all addresses on this domain have one owner)
- Custom domains can also be put in SPAM by very aggressive anti SPAM systems due to lack of reputation of newly registered domain (most commonly it is an issue only on new domains, and will disappear after some time)
- Custom domains have many information about you in WHOIS (can be removed, sometimes for additional price)
What will be recommended:
- Use public domains (to avoid being tied to one person if something will leak)
- Avoid catch-all. I know it is convenient but if someone will know your domain this person will be able to SPAM on random addresses on your domain and they will come to inbox.
- NEVER share main address. Ever. If you need something to be tied (ex bank) permanently, consider using separate address for it (for example additional mail address on Proton in the same account).
- For all conversations or signups for regular using use alias (including sending from alias)
- For everything like shops, cafes or other discount programs use temporary addresses. This also applies for everything you don’t trust.
I recommend Yopmail temporary addresses (they are most often permanent and supports forward and reply feature)