Problem reported by Mattias EngdegÄrd in:
https://lists.gnu.org/r/emacs-devel/2019-04/msg00543.html
* lisp/mail/mail-extr.el (mail-extr-telephone-extension-pattern):
Escape the trailing optional period after an abbreviation.
;; Matches telephone extensions.
(defconst mail-extr-telephone-extension-pattern
(purecopy
- "\\(\\([Ee]xt\\|[Tt]ph\\|[Tt]el\\|[Xx]\\).?\\)? *\\+?[0-9][- 0-9]+"))
+ "\\(\\([Ee]xt\\|[Tt]ph\\|[Tt]el\\|[Xx]\\)\\.?\\)? *\\+?[0-9][- 0-9]+"))
;; Matches ham radio call signs.
;; Help from: Mat Maessen N2NJZ <maessm@rpi.edu>, Mark Feit