Hello, background story (you can skip to the next paragraph for the actual feature request): I have a special "spam domain" with a catchall-email (all mails sent to my domain are forwarded to this email, unless there exists an actual account), so that I can give out customized email-adresses on the fly ("company_a@mydomain.org' to company A, "website_org@mydomain.org" when registering on website.org etc.) when I need to fill in an email address somewhere. This way, I can not only easily filter all unimportant mail to a secondary mailbox, but also see exactly where spammers got my email from. The problem now comes when I need to reply to such an email: As I of course don't edit my notmuch-config to adjust the other_email field everytime I invent such an email-address, notmuch doesn't know that the mail was written to me and thus puts in my standard email inside the from-header. I thus have to remember to manually change the from-header and put in the customized email. It would be much more convenient if I could teach notmuch that all adresses of some special form (for example written to some domain) are all mine and thus should be copied from the to-header to the from-header when replying. As far as I can see, there are at least two possible solutions: 1. (quick and dirty): Write a function which copies the to-header to the from-header if it matches some regular expression and call it from message-setup-hook. 2. (more general): Make the other_email field inside notmuch-config regular-expression aware (or maybe just support to indicate domain parts). This way, one could write something like other_email=@mydomain.org and notmuch would always copy the to-header to the from-header when replying to mails sent to something@mydomain.org I would be very thankful for any solution to this problem as it would save me a LOT of time every day. I tried to write a function for the message-setup-hook but due to my very limited knowledge of elisp and notmuch I didn't get it to work properly. Best, Simon