Forbiddance + Dismissal

[Soice]

Is it possible to use a dismissal spell inside a forbiddance spell area to send summoned monsters back where they came from? It is not on the list of descriptors and dismissal does not have a teleport subclass like the other spells listed.

[Kayerloth]

Yes, Dismissal used on a creature within the Forbiddance area will work normally. Forbiddance only prevents movement into or within the protected area. It does not prevent anyone or anything from using magic to leave the area by any means much less involuntarily via Dismissal. Bolding mine.

First paragraph of Forbiddance text wrote:

Forbiddance seals an area against all planar travel into or within it. This includes all teleportation spells (such as dimension door and teleport), plane shifting, astral travel, ethereal travel, and all summoning spells. Such effects simply fail automatically.