I am using catchall email adresses with my own domain.
For several purposes I have several adresses, p.ex. frdoid@mydomain.com, spam@mydomain.com, ebay@mydomain.com etc.
With thunderbird on Desktop, there is no issue. It chooses automatically the email adress the mail was sent to (p.ex. fdroid@mydomain.com) and uses it as the sender email.
Example: So if info@frdoid.com sends me an email to fdroid@mydomain.com and I want to answer, thunderbird will send the email from fdroid@mydomain.com. I never added fdroid@mydomain.com as a separate email account in thunderbird, I only set up catchall@mydomain.com.
The sender email fdroid@mydomain.com is automatically created as a sender address once a mail to a address abc(or whatever)@mydomain.com is received
I am now looking for an email client on android doing the same.