Email addresses containing '+' cannot be searched for

[waweber]

Version:

• listmonk: v6.2.0
• OS: Rocky Linux 10

Description of the bug and steps to reproduce:
Attempting to search for a subscriber containing a subaddress (user+subaddr@example.net) returns no results. Replacing with either \+ or a . (wildcard?) allows it to be searched. I can't seem to find concise documentation on how the search param works.

[mherzog4]

I traced this to the four subscriber query templates using PostgreSQL’s case-insensitive regex operator (~*) directly on the raw simple-search value. In that context, + is a quantifier, so user+subaddr@example.net does not search for a literal plus; other regex metacharacters can likewise change the query or make it invalid.

My proposed fix is backend-only: make the simple search parameter a case-insensitive literal substring comparison in the list, count, export, and bulk-action query templates, while leaving the separate advanced SQL-expression (query) feature unchanged. I’ll verify the normal substring behavior plus literal + and other metacharacters, and keep the PR scoped to this issue.