The structure of the IMAP tag is Axxxx, where:
- A is a letter (uppercase for conformity)
- x is a digit from 0 to 9
example of generated tag: T5439
It uses the class variable $this->currentTag.
Everytime it is called, the tag increases by 1.
If it reaches the last tag, it wraps around to the first tag.
By default, the first generated tag is A0001.