All notices to be given hereunder by either party shall be in writing, and shall be sent by certified mail, postage prepaid, addressed to the party intended to be notified. Notice given as aforesaid shall be a sufficient service thereof and shall be deemed given as of the date when deposited in any post office, or in any post office box regularly maintained by the Federal Government. Notice to Tenant and Landlord shall be sent to the following addresses or to such other person or to such other party as either party may from time to time designate in writing to the other.