Re means "regarding".
Re: regarding or in reference too
"re:" followed by subject content.
You're probably referring to the abbreviation for Date of Last Activity
The abbreviation "Re" is correct for the word "regarding" or as a prefix meaning "about". "RE" is commonly used in business correspondence as an abbreviation for "Regarding" or "Reference". Both are correct in different contexts.
"RE" in a letter stands for "regarding" or "in reference to." It is often used in the subject line to indicate the main topic or purpose of the letter.
WDW is most commonly used as an abbreviation for Walt Disney World in Florida. Although it could have other applications such as Worm Dragon Wing an online game it most often used regarding Disney.
ACTA is the abbreviation for the Association of Canadian Travel Agencies. ACTA was established in 1977 and is a non-profit organization.
Regarding the mail delivery system, IFR hasn't any meaning. This isn't a French postal code or abbreviation. That could probably be part of the name of the business you are writing to, or an internal abbreviation privvy to the sendee.
Are you sure it has anything to do with ferries?. Normally R.M.T.S was the abbreviation for the Royal Mail Turbine Steamers.
FTM is an abbreviation that stands for "Female-to-Male" and refers to transgender individuals. This means a person who was born genetically female but has transitioned -- or is in the process of transitioning -- to live as a male. Testosterone injections and surgeries may be a part of this transition.
ODThe medical abbreviations regarding the eye(s) are OD (Oculus Dexter, right eye), OS (Oculus Sinister, left eye), and OU (Oculus Uterque, both eyes).