It's usually best for a team to agree on a standardized glossary and a well-defined level of granularity for tracking and estimating, rather than defining these things on an individual basis. However, if you must go it alone, then generalizing activities into broad categories can be a useful technique.
Use Broad (But Meaningful) Categories When Possible
[N]ow I need to create a tag for the time I spent changing emails about minor details like issues, resource allocation and so on.
I'm not sure what you mean by "changing" emails, but in general I would lump this type of activity under one or more of the following categories:
- Project communications, because email is a form of communication.
- Project planning, because issues and resources affect plans and schedules.
- Issue tracking, because it sounds as if your team is using email as an issue tracker.
(NB: Whether or not this is a good idea is totally beside the point.)
Build Team Consensus Around Categories and Granularity
Of course, it doesn't really matter what strangers on the Internet think. This is a case where there isn't an objectively correct answer. Instead, you should work with your team (and specifically with your managers) to determine:
How they would like to see activities categorized.
Agreed-upon definitions that are standardized for your project are always more useful than ad-hoc labels. Standard categories improve communications and make the data more useful to management and for building accurate estimates.
What level of granularity they need in time tracking.
As discussed in this answer and in other questions, answers, and comments on this site, reporting should be done at a level that is useful. It may turn out that your time-tracking categories can be much more high-level than you assume...or possibly not. Either way, you won't know unless you ask.