Hashing algorithm used by OSX?
The passwords you find in Keychain Access are not hashed by OS X - you can view the actual password there.

44 characters could mean a 256 bit hash. If you base64 encode that, it would be 44 characters - with the last character being the equals sign (=).

However, there's no way to conclude which hash algorithm has been used for your password with only the two first starting characters.

For finding the original password, you could try various passwords you have used before, and run them through various hashing algoritms to compare. Alternative you could Google the hash or download rainbow tables to test with.

I would suggest simply trying to use what you think is a hash as the actual password to see if that works.

You might also be able to find more information in the documentation for the email client you have used.