Odinson
Hello,
Let me get right into this.
We use databases to store data that we want to have direct remote access to, something that allows us to have multiple "users" that can select, insert, update and delete data as fast as possible. That's what a database is for.
Each database contains multiple tables which contains multiple columns, these columns have types, values and indexes.
Once these are created, they're barely ever edited, so our job here is to make sure we think about this for the long run, to create something that, even if not used now, might be used in the future. Finally we can "easily" import your data to the database.
Everything else you mentioned though, such as sending emails and the import/export process itself aren't a feature of any database system (MySql, MariaDB, PostgreSql, etc). The database is just for storage, we're also gonna need to create a "tool", could be a web based one using PHP/HTML5 or a a local one using any programming language, which will then access the Database, do the necessary operations to "select" the clients and then send them an email, for example.
I know I talked too much about this but I think it's necessary you understand the process to. Now my job would be to make sure that ALL OF THIS is perfectly built and, with all humility, that's what I do and I'm very good at it...
I've handled big projects before, even here on Freelancer, check my reviews out, let me handle this.
Thanks for reading,
Mario Adabachy.