If there should be a single dot present which should not be at the start or right before the @, you could assert 13 characters followed by an @
^(?=[a-zçöşğü.]{13}@)[a-zçöşğü]+\.[a-zçöşğü]+@exm\.gov\.xx\.en$
In parts
^
Start of string
(?=
Positive lookahead, assert what is on the right is
[a-zçöşğü.]{13}@
Match 13 times any of the listed followed by an @
)
Close lookahead
[a-zçöşğü]+\.[a-zçöşğü]+
Match 2 times any of the listed with a dot inbetween
@exm\.gov\.xx\.en
Match @exm.gov.xx.en
$
End of string
Regex demo
Note that I have omitted the pipe |
from the character class as it would match it literally instead of meaning OR. If you meant to use it as a char, you could add it back. I also have remove the i
as that will be matched by a-z