Merge branch '462824-X-Delivered-To' into 'master'

Custom email: Add support for X-Delivered-To header

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/170221



Merged-by: Patrick Cyiza <jpcyiza@gitlab.com>
Approved-by: Marc Saleiko <msaleiko@gitlab.com>
Approved-by: Marcin Sedlak-Jakubowski <msedlakjakubowski@gitlab.com>
Approved-by: Patrick Cyiza <jpcyiza@gitlab.com>
Reviewed-by: Marc Saleiko <msaleiko@gitlab.com>
Co-authored-by: divyamtayal <divyamtayal18@gmail.com>