Use of Branding in Direct Mail

[Solomon Solomonov]

The expert consensus is that a campaign should include about 5-7 mailings. Statistics show the majority of the deals come from the 5th mailer and beyond. 

@Dev Horn has, on several occasions, stressed the importance of branding in direct mail campaigns in order to help stand out against competition. Moreover, @Jerry Puckett has advised that each subsequent mailer build on previous mailers (e.g. second mailer says "I have contacted you a few weeks back..."). These ideas make perfect sense if you want to create a campaign of 6 mailers, rather than 6 campaigns of one mailer. 

However, I would think that the synergies created would be lost if the recipient can't recognize a common brand from one mailer to the next. Yet, 1)  how does a homeowner distinguish two yellow letters sent from two different people (I'm not sure the name in the letter alone would do the trick)? 2) How can a homeowner recognize common brand between postcards and yellow letters? 

I am assuming several things here: the yellow letter is a handwritten letter the typical yellow paper. The only personal info of the sender included in the message is the name and phone number. There is no return address (according to @Michael Q., a return address could decrease the open rate). 

Any thoughts?