The email inside the a tag is the href of the a tag so just do this:
Using Selenium:
from selenium import webdriver
driver = webdriver.Firefox()
driver.get("http://somedomain/url_that_delays_loading")
a_tag = driver.find_element_by_id('MainCopy_ctl13_presentJob_EmailAddress')
mail_link = a_tag.get_attribute("href")
mail_addrs = mail_link.split(':')[1]
print(mail_addrs)
Using Beautifulsoup:
from bs4 import BeautifulSoup
content="""
<div id="MainCopy_ctl13_presentJob_EmailAddressPanel">
a id="MainCopy_ctl13_presentJob_EmailAddress" href="mailto:dburse@bjcta.org">xyzmmm@tccp.org</a>
</div>"""
soup = BeautifulSoup(content)
a_tag = soup.find(id='MainCopy_ctl13_presentJob_EmailAddress')
mail_link = a_tag.attrs['href']
mail_addrs = mail_link.split(':')[1]
print(mail_addrs)