The problem is that I make separate releases of the standalone email package from these branches, so that means that email 3.0.3 or 2.5.10 will have regressions.
Unless you're offering to also re-apply these changes after you make the Python releases <wink>.
If they are there primarily to track any changes that you want to release in the future (i.e. they are the repository of standalone email package), then a solution must be found, I agree.
Would it help if I branch branches/release23-maint/Lib/email to branches/email-2.3 ? Or should I branch the entire release23-maint to email-2.3? (branches are cheap in subversion) (*)
It would mean that you have to check in future 2.3 fixes of the email package into a different branch, and if you run into security fixes, you need to commit them into two branches (email-2.3 and release23-maint).
Same for 2.4. For 2.5, bug fixes could be added until that branch also goes into the security-only mode (i.e. after 2.6 is released).
Please let me know what you think.
(*) other locations are possible as well, such as branches/email/2.3 or /email/branches/2.3