i am also having this issue, macOS. It happened after compiling and installing the new sql files from this commit:
https://github.com/TrinityCore/TrinityCore/commit/309a7f7e2ab1f27a8c21d60791bcc6e5f7d6bec3
My server ran fine before this commit
I tried a fresh install on both Windows and macOS to be sure. This commit appears to have broken something. I think its still looking for mailtemplate instead of mailtemplateid (this commit dropped mailtemplate for mailtemplateid