Ms. Salutation for Two or More

Dear Dr. Dave and Dr. Dee,

When addressing envelopes, I know to separate names on the envelope when addressed to two unrelated people. But, when writing the letter, do I still separate the names if they have the same salutation? For example, do I write Dear Ms. Smith and Ms. Jones? If I use a plural, what is it for Ms.?

Signed,

Just inquiring

Dear Just inquiring,

It's fine to separate out Ms. for two women (Dear Ms. Smith and Ms. Jones). The plural for Ms. is Mses. or Mss., such as Dear Mses. Smith and Jones. For three or more persons, it's best to use a plural salutation.