Your colleague invites you to her wedding, by sending a personal email with the invitation card attached 

Response 1:

Open the email 

Read it

Reply back 

“Thanks <insert colleague name> 

Congratulations on your upcoming wedding. I am traveling and will unfortunately not be able to make it. Thanks for inviting me :)

Wishing you both a lovely wedding. All the best and God bless”

Response 2:

Open email

Open card

Read the details

Reply back 

“Thanks <insert colleague name>

Congratulations on your upcoming wedding. I am unfortunately traveling on the 19th and will be unable to make it. Sorry about that and thanks for inviting me 

Wish you and <insert bride’s name> a wonderful life ahead. All the best”

Time check

Response 2 > Response 1 by 10 seconds 

Respect check

Response 2 > Response 1 by infinity 

Respect doesn’t come from title. It comes from conduct.