3 separate studies: Hand addressed envelopes and hand written notes increase response by 300% over other direct mail methods.

Study 1: From: GETTING PERMISSION: EXPLORING FACTORS AFFECTING PERMISSION MARKETING, 2002 by Tito Tezinde, Brett Smith, Jamie Murphy Published in JOURNAL OF INTERACTIVE MARKETING VOLUME 16 / NUMBER 4 / AUTUMN 2002
(https://web.archive.org/web/20060822063725/https://web.biz.uwa.edu.au/staff/jmurphy/permission_jim.pdf)

Study 2: Gary L. Clark, Peter F. Kaminski, (1989) “How to Get More for Your Money in Mail Surveys”, Journal of Consumer Marketing, Vol. 6 Iss: 3, pp.45 – 51

Study 3: The IIW Institute of Information Management Dortmund / Langenfeld
Digital Printing Project Group Director: Prof. Dr. Carl B. Welker January 10, 2001 https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=10&ved=0CHAQFjAJ&url=http%3A%2F%2Fwww.edsf.org%2Ffile_download%2Ff7b27e49-8cba-4dcc-8037-ad3ab06373ee&ei=GDapUebHKZHy8ASHjYH4Ag&usg=AFQjCNHoA9WILBGeRvJBbDG05n7z37R5zA&sig2=aFDDHr7qq8sDT-AENf9paA

Industry Case Study: Handwritten marketing approach had 99.2% open rate.
A direct mail marketing company had an internal study where they compared handwritten solutions with seven of their other mailer options: including priority mail and attention grabbing envelopes (With labels like “Free money inside!” stamped on the envelope.) They included a free $25 dollar check in all the mailers and tracked results by the number of checks cashed. With 500 people in each test group – the handwritten solution was read by 99.2% or 496 people. The average read rate of the other 7 solutions was 34.2% (or) 171 out of 500.

Study: Handwritten signature in blue ink increased response rate by 21%
[Dodd, D. K., and Markweise, B. J. “Survey Response Rate as a Function of Personalized Signature on Cover Letter. Journal of Social Psychology. 127 (1987): 97–98]

Survey: 41% chooses hand addressed over all other option when “paying attention to an envelope and its contents”
(General Envelope Association – 2006 – “The envelope is more than a document cover, its your brand”)

Study: 64% of Americans prefer handwritten personal communication to electronic communication.
2006 Study by the Greeting Card Association

Study: Hand addressed envelopes are opened 72% more often than computer
generated addresses.
Association for conflict resolution, 2010 https://web.archive.org/web/20101123052225/https://www.mediate.com/acrconsumer/pg11.cfm
“The more personalized your piece, the more likely you are to receive a response. Make it easy for the recipient to contact you – attach a business card to every piece of mail you send. For additional attention, hand-write a post-script on the piece, on a post-it-note, or on the outside of the mailer (Use a colored ink pen and traditional yellow notes so that your recipient knows that you took the time to think about them and them alone). Also, hand-addressed envelopes are opened 72% more often than computer generated addresses.”

Study: Handwritten envelopes were the most likely envelope to be opened – drastically.
Pitney Bowes Mail Openability Study, Executive Summary, 1998
Note: Handwritten envelopes were the mostly likely to be opened out of 7 different study factors, so much so, they had to change the study to make it relevant to business models that weren’t likely to have envelopes so personalized.
“Note that consideration needed to be given to business mail (advertising, checks and bills) versus personal mail (correspondence from family and friends), and the overall weight given to (real) handwritten envelopes in openability was significant; a second model, without handwriting as a level of addressing techniques, was developed.”

Case Study: Handwritten envelopes for fundraising gets 50% donation response rate 2 years in a row and wins 3 marketing awards from the New England Direct Marketing Association.
A New Marketing Commentator, 2005, https://anewmarketingcommentator.com/2005/01/31/60

Case Study: Campaign raises 250% more with hand addressed envelope and note than other methods.
Beyond personalization: when handwriting makes a difference – Direct Marketing, May 1997, Volume: 60 Issue: 1 pp.60-61 (2 pages) https://www.emeraldinsight.com/bibliographic_databases.htm?id=1251134&show=abstract
“Union Gospel Mission used a hand-addressed invitation style card, that included a handwritten note asking for a special gift. The study notes that their Easter 1996 appeal achieved a 6.33:1 ROI, which compared to a more traditional window envelope package the same time the previous year (1995) that achieved only 2.39:1 ROI. A particularly interesting aspect of the article was the fact that even though the cost per piece for the handwritten campaign was higher, that did not matter, since the campaign raised more than 2 1/2 times more per dollar spent than the previous year’s package. Study calls results phenomenal.”

Case Study: Handwritten followup for lapsed donor renewal gets 9% to change mind
Chronicle of Philanthropy (May 16, 2002, p. 27).
The CARE campaign, according to the article, is driven by a simple handwritten note card. …It has a 34-word note on each card. Each envelope is then hand addressed and sent by first class mail. Each OSE and each CRE has a first class postage stamp affixed to it. The package includes a reply card and reply envelope. This campaign has been used for months.

“Hand addressed and hand written notes is an essential marketing technique.”
Direct Marketing for Nonprofits: Essential Techniques for the New Era (Aspen’s Fundraising Series for the 21st Century) – Dec. 2003
Direct Marketing Expert Kay Partney cites a case of using hand-addressed, hand-written note on a note card for New York’s Central Park Conservancy with great success. She teaches this method in her training book – direct marketing for nonprofits – as an essential marketing technique.

Case Study: Hand-written mailing doubles to triples response.
The Non-Profit Times, “A” in penmanship, 2001 NPT Publishing Group, Inc.
“Life Outreach International, based in Fort Worth, Texas, has used handwritten note cards successfully for a little more than six years, according to Vice President Terry Redmon.
LOI mails out one strictly handwritten mail piece a year, and it typically outperforms other correspondence mailings 2 to 1 and often as much as 3 to 1, considering the return on investment. Response rates have also been well above average during the three years — ranging between 7 percent and 20 percent, said Redmon.
“We have learned to utilize handwriting in other ways that have benefited our efforts that could be included in as many as six a year,” said Redmon.

Case Study: Feed the Children uses hand addressed thank you notes for their top donors. Get an additional 15% response rate.
The Non-Profit Times, “A” in penmanship, 2001 NPT Publishing Group, Inc.
“As for Larry Correa, vice president and chief information officer for Larry Jones International Ministries, Feed the Children in Oklahoma City, Okla., his organization has successfully mailed Christmas thank-you note cards/appeals to its $1,000 and above donors the past three years.
“We use them as an appeal. … It’s our last appeal at Christmas time,” said Correa. “It drops on December 25 to get that very last donation from the donor.”
The 2000 Christmas time, thank-you note card mailing, which is mailed to roughly 100,000 higher-end donors, garnered an outstanding 15 percent response rate.
And although Correa would not divulge average gift sizes, he said the note card, with hand-written addressed envelope, personalized typed note, and hand-written P.S., is the main reason the nonprofit continues the mailing.”

How to get a 50% response rate…a handwritten note.
Direct Mail Strategies: How To Get a 50% D.M. Response Rate With A Stroke Of The Pen – By Michael Kaselnak owner of frugal marketing — https://www.frugalmarketing.com/dtb/stroke-of-the-pen.shtml
“That tool is a simple handwritten note.
A Midwestern restaurant owner sent out a series of handwritten notes to his customers and had a 20% response rate.
A financial planner in the Northeast sent out just 80 handwritten notes to touch base with prospects and had 6 people call him and 2 set appointments.
A non-profit was able to get 51 donations by simply sending a handwritten note to warm list of 100 people.
Why?
Handwritten notes are special. Clients cannot throw them away without reading them.
I dare you to try and throw out a handwritten note without reading it the next time you get one.”

Guerilla marketing non-profit increases response rate by 668% with handwritten mail
When to halt a marketing attack – by Jay Conrad Levison – https://www.gmarketing.com/articles/15-when-to-halt-a-marketing-attack
“The benefit of precision is that it allows you to get personal. Recall the non-profit organization that increased its response rate 668% by treating its big donors special — mailing to them with a handwritten envelope using a commemorative stamp and a handwritten 25-word note at the end of the letter. The cost to do this was low, indeed. But the payoff proved the value of precision and narrow-mindedness in a guerrilla marketing attack. Precision and constancy. Those are your allies.”
3 separate studies: Hand addressed envelopes and hand written notes increase response by 300% over other direct mail methods.

Study 1: From: GETTING PERMISSION: EXPLORING FACTORS AFFECTING PERMISSION MARKETING, 2002 by Tito Tezinde, Brett Smith, Jamie Murphy Published in JOURNAL OF INTERACTIVE MARKETING VOLUME 16 / NUMBER 4 / AUTUMN 2002
(https://web.archive.org/web/20060822063725/https://web.biz.uwa.edu.au/staff/jmurphy/permission_jim.pdf)

Study 2: Gary L. Clark, Peter F. Kaminski, (1989) “How to Get More for Your Money in Mail Surveys”, Journal of Consumer Marketing, Vol. 6 Iss: 3, pp.45 – 51

Study 3: The IIW Institute of Information Management Dortmund / Langenfeld
Digital Printing Project Group Director: Prof. Dr. Carl B. Welker January 10, 2001 https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=10&ved=0CHAQFjAJ&url=http%3A%2F%2Fwww.edsf.org%2Ffile_download%2Ff7b27e49-8cba-4dcc-8037-ad3ab06373ee&ei=GDapUebHKZHy8ASHjYH4Ag&usg=AFQjCNHoA9WILBGeRvJBbDG05n7z37R5zA&sig2=aFDDHr7qq8sDT-AENf9paA

Industry Case Study: Handwritten marketing approach had 99.2% open rate.
A direct mail marketing company had an internal study where they compared handwritten solutions with seven of their other mailer options: including priority mail and attention grabbing envelopes (With labels like “Free money inside!” stamped on the envelope.) They included a free $25 dollar check in all the mailers and tracked results by the number of checks cashed. With 500 people in each test group – the handwritten solution was read by 99.2% or 496 people. The average read rate of the other 7 solutions was 34.2% (or) 171 out of 500.

Study: Handwritten signature in blue ink increased response rate by 21%
[Dodd, D. K., and Markweise, B. J. “Survey Response Rate as a Function of Personalized Signature on Cover Letter. Journal of Social Psychology. 127 (1987): 97–98]

Survey: 41% chooses hand addressed over all other option when “paying attention to an envelope and its contents”
(General Envelope Association – 2006 – “The envelope is more than a document cover, its your brand”)

Study: 64% of Americans prefer handwritten personal communication to electronic communication.
2006 Study by the Greeting Card Association

Study: Hand addressed envelopes are opened 72% more often than computer
generated addresses.
Association for conflict resolution, 2010 https://web.archive.org/web/20101123052225/https://www.mediate.com/acrconsumer/pg11.cfm
“The more personalized your piece, the more likely you are to receive a response. Make it easy for the recipient to contact you – attach a business card to every piece of mail you send. For additional attention, hand-write a post-script on the piece, on a post-it-note, or on the outside of the mailer (Use a colored ink pen and traditional yellow notes so that your recipient knows that you took the time to think about them and them alone). Also, hand-addressed envelopes are opened 72% more often than computer generated addresses.”

Study: Handwritten envelopes were the most likely envelope to be opened – drastically.
Pitney Bowes Mail Openability Study, Executive Summary, 1998
Note: Handwritten envelopes were the mostly likely to be opened out of 7 different study factors, so much so, they had to change the study to make it relevant to business models that weren’t likely to have envelopes so personalized.
“Note that consideration needed to be given to business mail (advertising, checks and bills) versus personal mail (correspondence from family and friends), and the overall weight given to (real) handwritten envelopes in openability was significant; a second model, without handwriting as a level of addressing techniques, was developed.”

Case Study: Handwritten envelopes for fundraising gets 50% donation response rate 2 years in a row and wins 3 marketing awards from the New England Direct Marketing Association.
A New Marketing Commentator, 2005, https://anewmarketingcommentator.com/2005/01/31/60

Case Study: Campaign raises 250% more with hand addressed envelope and note than other methods.
Beyond personalization: when handwriting makes a difference – Direct Marketing, May 1997, Volume: 60 Issue: 1 pp.60-61 (2 pages) https://www.emeraldinsight.com/bibliographic_databases.htm?id=1251134&show=abstract
“Union Gospel Mission used a hand-addressed invitation style card, that included a handwritten note asking for a special gift. The study notes that their Easter 1996 appeal achieved a 6.33:1 ROI, which compared to a more traditional window envelope package the same time the previous year (1995) that achieved only 2.39:1 ROI. A particularly interesting aspect of the article was the fact that even though the cost per piece for the handwritten campaign was higher, that did not matter, since the campaign raised more than 2 1/2 times more per dollar spent than the previous year’s package. Study calls results phenomenal.”

Case Study: Handwritten followup for lapsed donor renewal gets 9% to change mind
Chronicle of Philanthropy (May 16, 2002, p. 27).
The CARE campaign, according to the article, is driven by a simple handwritten note card. …It has a 34-word note on each card. Each envelope is then hand addressed and sent by first class mail. Each OSE and each CRE has a first class postage stamp affixed to it. The package includes a reply card and reply envelope. This campaign has been used for months.

“Hand addressed and hand written notes is an essential marketing technique.”
Direct Marketing for Nonprofits: Essential Techniques for the New Era (Aspen’s Fundraising Series for the 21st Century) – Dec. 2003
Direct Marketing Expert Kay Partney cites a case of using hand-addressed, hand-written note on a note card for New York’s Central Park Conservancy with great success. She teaches this method in her training book – direct marketing for nonprofits – as an essential marketing technique.

Case Study: Hand-written mailing doubles to triples response.
The Non-Profit Times, “A” in penmanship, 2001 NPT Publishing Group, Inc.
“Life Outreach International, based in Fort Worth, Texas, has used handwritten note cards successfully for a little more than six years, according to Vice President Terry Redmon.
LOI mails out one strictly handwritten mail piece a year, and it typically outperforms other correspondence mailings 2 to 1 and often as much as 3 to 1, considering the return on investment. Response rates have also been well above average during the three years — ranging between 7 percent and 20 percent, said Redmon.
“We have learned to utilize handwriting in other ways that have benefited our efforts that could be included in as many as six a year,” said Redmon.

Case Study: Feed the Children uses hand addressed thank you notes for their top donors. Get an additional 15% response rate.
The Non-Profit Times, “A” in penmanship, 2001 NPT Publishing Group, Inc.
“As for Larry Correa, vice president and chief information officer for Larry Jones International Ministries, Feed the Children in Oklahoma City, Okla., his organization has successfully mailed Christmas thank-you note cards/appeals to its $1,000 and above donors the past three years.
“We use them as an appeal. … It’s our last appeal at Christmas time,” said Correa. “It drops on December 25 to get that very last donation from the donor.”
The 2000 Christmas time, thank-you note card mailing, which is mailed to roughly 100,000 higher-end donors, garnered an outstanding 15 percent response rate.
And although Correa would not divulge average gift sizes, he said the note card, with hand-written addressed envelope, personalized typed note, and hand-written P.S., is the main reason the nonprofit continues the mailing.”

How to get a 50% response rate…a handwritten note.
Direct Mail Strategies: How To Get a 50% D.M. Response Rate With A Stroke Of The Pen – By Michael Kaselnak owner of frugal marketing — https://www.frugalmarketing.com/dtb/stroke-of-the-pen.shtml
“That tool is a simple handwritten note.
A Midwestern restaurant owner sent out a series of handwritten notes to his customers and had a 20% response rate.
A financial planner in the Northeast sent out just 80 handwritten notes to touch base with prospects and had 6 people call him and 2 set appointments.
A non-profit was able to get 51 donations by simply sending a handwritten note to warm list of 100 people.
Why?
Handwritten notes are special. Clients cannot throw them away without reading them.
I dare you to try and throw out a handwritten note without reading it the next time you get one.”

Guerilla marketing non-profit increases response rate by 668% with handwritten mail
When to halt a marketing attack – by Jay Conrad Levison – https://www.gmarketing.com/articles/15-when-to-halt-a-marketing-attack
“The benefit of precision is that it allows you to get personal. Recall the non-profit organization that increased its response rate 668% by treating its big donors special — mailing to them with a handwritten envelope using a commemorative stamp and a handwritten 25-word note at the end of the letter. The cost to do this was low, indeed. But the payoff proved the value of precision and narrow-mindedness in a guerrilla marketing attack. Precision and constancy. Those are your allies.”