[exim] Dumb DNS question about MX records.

Is this set of records legal? My ISP claims it will break something if they
implement it:

mail.interclean.com.   MX  30  mail.interclean.com.
mail.interclean.com.   A       152.160.178.33

I realize it should be *unnecessary*, but will it work?

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David Brodbeck, System Administrator
InterClean Equipment, Inc.
3939 Bestech Drive Suite B
Ypsilanti, MI 48197
(734) 975-2967 x221
(734) 975-4756 (fax)