Why is my program only using the last if statement?

I'm kinda new to python and tried to write a little email client. The goal is to select your favorite email service and login into your email. I'm using if statements to select the respective smtp server / email service. But it seems not to work, my program is always selecting the last statement and i dont have a clue to fix it. ( the ability to send emails is not finished yet) I would also be thankfull for some ideas about a new method to select the specific smtp server :)

from tkinter import *
from tkinter import ttk
import smtplib
import tkinter as tk
import ssl


fenster       = Tk()
fenster.title('ITA-Projekt') 
fenster.geometry('330x280') 


tabControl = ttk.Notebook(fenster)
tab1 = ttk.Frame(tabControl) 
tab2 = ttk.Frame(tabControl) 

tabControl.add(tab1, text ='Login') 
tabControl.add(tab2, text ='Email verfassen')  

#Auswahl Liste 

Liste = [
"Gmail",
"Yahoo mail",
"GMX",
"Web.de",
]

auswahl_var = tk.StringVar(tab1)
auswahl_var.set(Liste[0])

opt = tk.OptionMenu(tab1, auswahl_var, *Liste)
opt.config(width=8,height=0)
opt.place(x=215, y=10)



#Tab1 

LoginEntry = ttk.Entry(tab1, show="*")
EmailEntry = ttk.Entry(tab1)

LoginLabel = ttk.Label(tab1,text='Passwort:')
LoginLabel.grid(row=1, column=0)

EmailLabel = ttk.Label(tab1,text='Email:')
EmailLabel.grid(row=0, column=0)

LoginEntry.grid(row=1, column=2, padx=15, pady=15)
EmailEntry.grid(row=0, column=2, padx=15, pady=15)

#buttonLogin = ttk.Button(tab1, text="Login", command=Einloggen)
#buttonLogin.place(x=90, y=140)


buttonAusloggen = ttk.Button(tab1, text="Ausloggen")
buttonAusloggen.place(x=90, y=170)


tabControl.pack(expand = 1, fill ="both") 


def Einloggen():

 Email = EmailEntry.get()
 Passwort = LoginEntry.get()

 if (auswahl_var == "Gmail"):
    smtp_objekt = smtplib.SMTP('smtp.gmail.com', 587)
    smtp_objekt.ehlo()
    smtp_objekt.starttls()
    smtp_objekt.ehlo()
    smtp_objekt.login(Email, Passwort)

   else:

     if (auswahl_var == "Yahoo mail"):
        server = smtplib.SMTP('smtp.mail.yahoo.com', 587)
        server.ehlo()
        server.starttls()
        server.ehlo()
        server.login(Email, Passwort) 

       else:

         if (auswahl_var == "GMX"):
            server = smtplib.SMTP('smtp.gmail.com', 587)
            server.ehlo()
            server.starttls()
            server.ehlo()
            server.login(Email, Passwort)
           else:

            server = smtplib.SMTP('smtp.web.de', 587)
            server.ehlo()
            server.starttls()
            server.ehlo()
            server.login(Email, Passwort)   



 buttonLogin = ttk.Button(tab1, text="Login", command=Einloggen)
 buttonLogin.place(x=90, y=140)


#Tab2 

EmpfEntry = ttk.Entry(tab2)
BetreffEntry = ttk.Entry(tab2)
BodyEntry = ttk.Entry(tab2)

EmpfLabel = ttk.Label(tab2,text='Empfänger:')
EmpfLabel.grid(row=0, column=0)

BetreffLabel = ttk.Label(tab2,text='Betreff:')
BetreffLabel.grid(row=1, column=0)

EmpfEntry.grid(row=1, column=2, padx=15, pady=15)
BetreffEntry.grid(row=0, column=2, padx=15, pady=15)
BodyEntry.grid(row=2, column=2, padx=15, pady=15)

buttonSenden= ttk.Button(tab2, text="Senden")
buttonSenden.place(x=90, y=140)



fenster.mainloop()